Disease and Pest Management – News https://doubleavineyards.com/news Fri, 15 Jul 2022 11:44:17 +0000 en-US hourly 1 https://wordpress.org/?v=6.4.1 How To Select and Use Crop Protection Products in an Integrated Vineyard Pest Management Program https://doubleavineyards.com/news/how-to-select-and-use-crop-protection-products-in-an-integrated-vineyard-pest-management-program/ Mon, 24 Jun 2019 18:18:41 +0000 https://doubleavineyards.com/blog/?p=70 Rick Dunst, Viticulturist, Double A Vineyards, Inc.

Double A Vineyards offers a full line of crop protection products available to our customers. There are several grape diseases that can cause crop loss directly, through infection of fruit, or indirectly, through loss of leaf area. Various insects feed on grape flowers, fruit, leaves, and roots, resulting in decreased productivity. Weeds can compete with grapevines for water and nutrients resulting in reduced vine capacity. While the use of cultural methods of pest control are encouraged, responsible use of pesticides is often necessary to produce full yields of high quality fruit. This article will discuss how the crop protection products we offer can be integrated into a pest management program for grapes, and offers sample disease management programs for three grape cultivars with varying levels of disease susceptibility.

The Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) recognizes two classifications of pesticides: general use and restricted use. While general use pesticides can be purchased and used by anyone, only certified pesticide applicators can purchase and use (or supervise the use of) restricted use pesticides. Double A Vineyards offers only general use pesticides that are not classified as restricted use either federally or in New York State. It is the user’s responsibility to observe all restrictions and requirements pertinent to local, state, and federal guidelines concerning the use of these pesticides, including use of personal protective equipment (PPE), transportation, storage, and record keeping of pesticides. Information about requirements can be found through local or regional Cooperative Extension programs. Businesses that hire employees to handle or apply pesticides, or work in pesticide-treated crops, must also meet EPA Worker Protection Standard requirements, which may include restricted-entry intervals (REIs), use of personal protective equipment (PPE), pesticide safety training and posting, decontamination supplies, and emergency assistance. Complete information about the WPS can be found at www.epa.gov/pesticides/health/worker.htm.

Developing an effective vineyard pest management program requires an understanding of several factors including pest biology, the mode of action of pesticides used in pest management, and varietal susceptibility to vineyard pests. University and private consultant vineyard pest management guides are an important source of information, but pesticide labels can change, and it is the user’s responsibility to read and understand the label of the pesticide product being used. “Read the label, the label is the law.”

There are many sources of information that can be used to develop a vineyard pest management program, including:

 

FUNGICIDES 

Fungicide efficacy in controlling the major diseases of grapes is listed in the following table:

Fungicide Chart

Mancozeb fungicide (Manzate Pro-Stick) is considered the backbone of many disease management programs in grapes. Mancozeb provides protectant control of black rot, downy mildew, and Phomopsis. It is a broad-spectrum fungicide with low risk of disease resistance development.

Manzate Pro-Stick Fungicide 30 lbs (mancozeb), EPA# 70506-234, READ THE LABEL

Manzate Pro-Stick Fungicide 6 lbs (mancozeb), EPA# 70506-234, READ THE LABEL

Apply Manzate Pro-Stick at 1.5 to 4 lb per acre per application, do not apply more than 24 lb per acre per season. If applied at its maximum use rate (4 lb/acre), a 30 lb bag will cover 7.5 acres of vineyard with a single application, a 6 lb bag will cover 1.5 acres with a single application, and may be applied up to 6 times per season. 24 hour REI, 66 day PHI.

Note: Dithane F-45 is now a restricted use product in New York and is no longer offered by Double A Vineyards.  It is not restricted use at the federal level.

CAPTAN 50 Wettable Powder (captan), EPA# 66330-234, READ THE LABEL

Captan provides protective control of Phomopsis, downy mildew, and various “summer rots”. It also provides some control of black rot, but mancozeb and ziram are better choices for protective control of black rot under high disease pressure. It is a broad-spectrum fungicide with low risk of disease resistance development. Apply 2 to 4 lb of Captan 50 WP per acre per application, do not apply more than 24 lb per acre per season. Apply Captan 50 WP at 4 lb per acre for control of downy mildew, or at 2 to 4 lb per acre for control of Phomopsis. Do not apply with or following a spray of JMS Stylet Oil, and do not apply JMS stylet oil within 10 days of application. Captan can cause plant injury if applied with other oils, liquid insecticides, and some surfactants. Fungicide activity can be reduced if applied with lime. If applied at its maximum use rate of 4 lb per acre, a 4 lb bag of Captan 50 WP will cover 1 acre of vineyard with a single application, and may be applied up to 6 times per season. 72 hour REI, 0 day PHI. Maximum purchase 3 – 5 lb bags per DOT ground shipping regulations.

Captan 80WDG (captan), EPA# 66222-58-66330, READ THE LABEL

Captan provides protective control of Phomopsis, downy mildew, and various “summer rots”. It also provides some control of black rot, but mancozeb and ziram are better choices for protective control of black rot under high disease pressure. It is a broad-spectrum fungicide with low risk of disease resistance development. Apply 1.25 to 2.5 lb of Captan 80 WDG per acre per application, do not apply more than 15 lb per acre per season. Apply Captan 80 WDG at 2.5 lb per acre for control of downy mildew, or at 1.25 to 2.5 lb per acre for control of Phomopsis. Do not apply with or following a spray of JMS Stylet Oil, and do not apply JMS stylet oil within 10 days of application. Captan can cause plant injury if applied with other oils, liquid insecticides, and some surfactants. Fungicide activity can be reduced if applied with lime. Maximum purchase 1 – 6.25 lb bag per DOT ground shipping regulations. If applied at its maximum use rate of 2.5 lb per acre, a 6.25 lb bag will cover 2.5 acres of vineyard with a single application, and may be used up to 6 times per season. 72 hour REI, 0 day PHI. Maximum purchase 1 – 6.25 lb. bag per DOT ground shipping regulations.

Captec 4L (captan), EPA# 66330-239, READ THE LABEL

Captan provides protective control of Phomopsis, downy mildew, and various “summer rots”. It also provides some control of black rot, but mancozeb and ziram are better choices for protective control of black rot under high disease pressure. It is a broad-spectrum fungicide with low risk of disease resistance development. Apply 1 to 2 qt per acre per application, do not apply more than 12 qt per season. Apply Captec 4L at 2 qt per acre for control of downy mildew, or at 1-2 qt per acre for control of Phomopsis. Do not apply with or following a spray of JMS Stylet Oil, and do not apply JMS stylet oil within 10 days of application. Captan can cause plant injury if applied with other oils, liquid insecticides, and some surfactants. Fungicide activity can be reduced if applied with lime. If applied at its maximum use rate of 2 qt per acre, a 2.5 gal container will cover 5 acres of vineyard with a single application, and may be used up to 6 times per season. This product can only be shipped by LTL as per DOT regulations. LTL shipments require a fork lift for unloading at your location, or pickup at a Fed-Ex warehouse. 48 hour REI, 0 day PHI.

Ziram 76DF Fungicide (ziram), 40 lb. bag EPA# 70506-173, READ THE LABEL

Ziram Xcel Fungicide (ziram), 6 lb. bag EPA# 70506-173, READ THE LABEL

Ziram provides protective control of black rot and Phomopsis. It also provides some control of downy mildew, but mancozeb and captan are better choices for protective control of downy mildew under high disease pressure. It is a broad-spectrum fungicide with low risk of disease resistance development. Apply Ziram 76DF at 3-4 lb per acre per application at 7-14 day intervals, do not apply more than 28 lb per acre per season. If applied at its maximum use rate of 4 lb per acre, a 6 lb bag of Ziram Xcel will cover 1.5 acres of vineyard in a single application, a 40 lb bag of Ziram 76DF will cover 10 acres of vineyard in a single application, and may be used up to 7 times per season. 48 hour REI, 21 day PHI.

 

Synthetic fungicides for (primarily) powdery mildew control

Double A Vineyards offers 4 different chemical groups that control the powdery mildew fungus via different modes of action. These chemical groups include:

1) The sterol inhibitor (SI), or DMI fungicides, including tebuconazole (TebuStar 45WSP®), Rally®, Mettle®, and Revus Top®.
2) The strobilurin fungicides, including Abound® and Pristine®.
3) The azanaphthaline (quinioline) fungicide Quintec®, and
4) The benzphenone fungicide Vivando®.

The powdery mildew fungus is extremely prone to the development of disease resistant strains. Once powdery mildew resistance develops to a specific fungicide, that fungicide, AS WELL AS OTHER FUNGICIDES IN THE SAME CHEMICAL FAMILY, should no longer be depended upon to control the disease. For this reason, the use of fungicides in two or (preferably) more chemical groups effective in controlling powdery mildew should be used in a rotational program in order to delay or prevent the onset of the development of resistance. Within limitations, post-infection fungicides can be tank-mixed with synthetic fungicides to help eradicate disease once it has begun to establish. Refer to Disease Program for Grapes – Part I : Grapevine diseases and early considerations and Disease Program for Grapes – Part II : Managing grape diseases from bloom through harvest for additional information.

TebuStar 45WSP (tebuconazole), EPA# 42750-102, READ THE LABEL

Tebuconazole provides effective control of powdery mildewand black rot with post-infection, antisporulant, and limited protectant activity, with moderate risk of disease resistance development. Apply TebuStar at 4 oz. per acre per application and a maximum or 2 pounds per season. For powdery mildew control, apply on a protective schedule with applications made 14 days (preferable in mostcircumstances) to 21 days apart. For black rot control, apply on a 7 to 14 day schedule, OR within 72 hours of the start of an infection period, but not within 7 days of a previous application. Tebuconazole is a sterol inhibitor (DMI) fungicide, and powdery mildew resistance to the DMI fungicidesis common where they have been used for several years. Use a good resistance management strategy in your vineyard by limiting the number of DMI applications to a maximum of 3 per year, and use a rotational program with other non-DMI powdery mildew fungicides. Rotating with other DMI fungicidesis NOT an effective disease resistance management approach. 12 hour reentry interval, 14 days to harvest.

Rally 40WSP (myclobutanil), EPA# 62719-410, READ THE LABEL

Rally provides effective control of powdery mildew, black rot, and anthracnose with post-infection, antisporulant, and limited protectant activity, with moderate risk of disease resistance development. Apply Rally at 3-5 oz per acre per application and a maximum of 1.5 pounds per season (typical application rates used in New York are 4 oz per acre for protection, and 5 oz per acre for post-infection control of black rot). Apply on a protectant schedule that does not exceed 14 days, or within 72 hours of a black rot infection period. Rally is a sterol inhibitor (DMI) fungicide, and powdery mildew resistance to the DMI fungicides is common where they have been used for several years. Use a good resistance management strategy in your vineyard by limiting the number of DMI applications to a maximum of 3 per year, and use in a rotational program with other non-DMI powdery mildew fungicides. Rotating with other DMI fungicides is NOT an effective disease resistance management approach. If applied at the powdery mildew control rate of 4 oz per acre, a 20 oz container will cover 5 acres of vineyard with a single application. Although the label permits the use of 1.5 lb product per season (6 applications at the 4 oz rate), it is highly recommended that a maximum of 3 applications of all DMI fungicides be used per season in a rotation with other effective powdery mildew fungicides. This product is sold as a 20 oz package containing 5 – 4 oz water soluble packets. 12 hour REI, 14 day PHI.

Mettle 125 ME Fungicide (tetraconazole), EPA# 80289-8, READ THE LABEL

Mettle provides effective control of black rot, anthracnose, and powdery mildew with post-infection, antisporulant, and limited protectant activity, with moderate risk of disease resistance development. Apply Mettle at 3 to 5 fl oz per acre per application and a maximum of 3 applications and 10 fl oz.per season. For powdery mildew control, apply on a protective schedule with applications made 14 days (preferable in most circumstances) to 21 days apart. For black rot control, apply on a 14 day schedule, OR within 72 hours of the start of an infection period, but not within 14 days of a previous application. Tebuconazole is a sterol inhibitor (DMI) fungicide, and powdery mildew resistance to the DMI fungicides is common where they have been used for several years. Use a good resistance management strategy in your vineyard by limiting the number of DMI applications to a maximum of 3 per year, and use a rotational program with other non-DMI powdery mildew fungicides. Rotating with other DMI fungicides is NOT an effective disease resistance management approach. If applied at its recommended use rate of 3 to 5 fl oz. per acre, a 30 fl oz container will spray 6 to 10 acres of vineyard with a single application. 12 hour REI (7 day reentry for certain activities in table grapes), 14 day PHI.

Revus Top (difenoconazole + mandipropamid), EPA# 100-1278, READ THE LABEL

Revus Top contains two unrelated active ingredients, difenoconazole and manipropamid, with a moderate risk of disease resistance development. Difenoconazole is a sterol inhibitor (DMI) fungicide that provides very good to excellent activity against powdery mildew, black rot, and anthracnose with limited protectant, post-infection, and antisporulant activity, with moderate risk of disease resistance development. Manipropamid, the active ingredient in Revus, provides excellent control of downy mildew with protectant, some post-infection, and perhaps some antisporulant activity, with moderate risk of disease resistance development. Apply Revus Top at 7 fl oz per acre per application, and no more than 28 fl oz per acre per season. Add a non-ionic/penetrating surfactant as per label instructions. Make no more than 2 consecutive applications before switching to other fungicides effective against powdery mildew and downy mildew. Rotating with other DMI fungicides is NOT an effective disease resistance management approach. Evaluations by Wayne Wilcox, Cornell University, indicate that the DMI component in Revus Top, difenoconazole, is much more active against powdery mildew than the other DMI fungicides. However, note that Revus Top cannot be used on Concord, Concord Seedless, and Thomcord (causes injury) and that injury may occur on certain other native and hybrid cultivars including Brianna, Canadice, Frontenac, Glenora, Noiret, Skujinsh 675, and St. Croix. Injury is worse when the fungicide is mixed with surfactants or other oils that promote absorption into the vines. Although the label permits the use of 28 fl oz per season (4 applications at the 7 oz rate), it is highly recommended that a maximum of 3 applications of all DMI fungicides be used per season in a rotation with other effective powdery mildew fungicides. If applied at its use rate of 7 oz per acre, a 2.5 gallon container of Revus Top will cover 45.7 acres of vineyard with a single application. 12 hour REI, 14 day PHI.

Abound Flowable Fungicide (azoxystrobin), EPA# 100-1098, READ THE LABEL

Abound provides very effective control of powdery mildew, downy mildew, and black rot, moderate control of Phomopsis, and slight control of Botrytis, with a high risk of disease resistance development. Apply Abound at 10 to 15.5 fl oz per acre. Abound is a strobilurin fungicide, and powdery mildew and downy mildew resistance to the strobilurins is known to occur widely in the Eastern United States. A maximum of 92.3 fl oz of product can be used per season, consult the label for details. Do not use more than 2 sequential applications. It is highly recommended to limit applications of strobilurin fungicides to a maximum of 2 per season, rotate them with other unrelated fungicides, and tank mix with sulfur on non-sulfur-sensitive varieties. If applied at a typical use rate of 11 to 15 fl oz per acre, a 1 gal container of Abound will cover 8.5 to 11.6 acres of vineyard with a single application.  IMPORTANT NOTE: Abound is EXTREMELY phytotoxic to certain apple varieties. Do not spray Abound where spray drift may reach apple trees. Do not use spray equipment which has been previously used to apply Abound to spray apple trees, as even trace amounts can cause unacceptable phytotoxicity to certain apple and crabapple varieties. Use of Abound through airblast application equipment on grapes is prohibited in the following townships and boroughs of Erie County, Pennsylvania: North East, Harborcreek, Lawrence Park, Erie, Presque Isle, MillCreek, Fairview, Girard, and Springfield – this prohibition is intended to help eliminate phytotoxicity problems with apples observed in this geographic location. 4 hour REI, 14 day PHI.

Pristine Fungicide (pyraclostrobin + boscalid), EPA#7969-199, READ THE LABEL

Pristine contains two unrelated active ingredients, pyraclostrobin and boscalid, with a high risk of disease resistance development. Pyraclostrobin is a strobilurin fungicide that provides excellent activity against downy mildew and powdery mildew, very good activity against black rot, some activity against Phomopsis, and fair activity against Botrytis at higher rates. It also provides very good control of bitter rot and ripe rot, and some suppression of the sour rot disease complex. Boscalid provides excellent control of powdery mildew, and fair to excellent control of Botrytis, depending on the use rate. Thus, Pristine provides excellent control of downy mildew, powdery mildew, and black rot, fair to good control of Phomopsis, fair control of Botrytis at the 8 to 12.5 oz per acre application rate, and good to excellent control of Botrytis at the 19 oz per acre rate. Pristine is phytotoxic on Concord and Noiret, so should not be used on these varieties. It should also be used with caution on Steuben and Rougheon, where injury has occurred irregularly. Powdery mildew and downy mildew resistance to the strobilurin fungicides is known to occur widely in the Eastern United States. The boscalid component of Pristine is also at risk for powdery mildew resistance development. In order to minimize the resistance development of Pristine where it has not already occurred, limit applications of Pristine and strobilurin fungicides to a maximum of 2 per season, rotate them with other unrelated fungicides, and tank mix with sulfur on non-sulfur-sensitive varieties. Pristine is sold as a 7.5 lb. (120 oz.) container, so a container will spray approximately 6 to 15 acres of vineyard with a single application, depending on the application rate. 12 hour/5 day REI (see label for details), 14 day PHI.

Quintec (quinoxyfen), EPA# 62719-375, READ THE LABEL

Quintec provides excellent protectant control but no post-infection or eradicant control of powdery mildew, with moderate risk of disease resistance development. Apply at 3 to 6.6 fl oz per acre per application (the 3 to 4 fl oz rate is recommended in New York State at no more than 14 day intervals), and no more than 33 fluid ounces per acre per season. Quintec is unrelated to any other grape fungicide registered in North America, so it controls powdery mildew colonies that are resistant to other fungicides and is useful in a powdery mildew resistance-management program. However, Quintec is at risk for disease resistance development, so it should be used no more than 2 or 3 times per season in a rotational program with other effective powdery mildew fungicides. If applied at a typical use rate of 4 fl oz per acre, a 30 fl oz container will cover 7.5 acres of vineyard with a single application. 12 hour REI, 14 day PHI.

Vivando Fungicide (metrafenone), EPA# 7969-284, READ THE LABEL

Vivando provides excellent control of powdery mildew with protectant, post-infection, and antisporulant activity, with moderate to high risk of disease resistance development. Apply at 10.3 to 15.4 fl oz per acre per application on a 14 to 21 day schedule (use of the lower rate on a 14 day schedule is typical in New York State), and no more than 46.2 fl oz per acre per season. Do not make more than 2 sequential applications before alternating with another effective powdery mildew fungicide, and do not make more than 3 applications per season. The minimum interval between applications is 14 days. Vivando is unrelated to any other fungicide product currently in the market, so use in a rotational program with other effective powdery mildew fungicides is a good resistance management strategy. If applied at the low use rate of 10.3 fl oz per acre, a 1 gallon container will cover 12.4 acres of vineyard with a single application. 12 hour REI, 14 day PHI.

___________________________________________________________________

 

Additional Fungicides

Ranman Fungicide 50 WG (cyazofamid), EPA# 71512-3-279, READ THE LABEL

Ranman provides good to very good control of downy mildew with protectant, antisporulant, and perhaps limited post-infection activity, with high risk of disease resistance development. Ranman represents a new class of chemistry for use in grapes, and should be used in a rotational program with other downy mildew fungicides. Apply at 2.1 to 2.75 fl oz per acre per application, and no more than 6 applications per season. Alternate Ranman with another downy mildew fungicide with a different mode of action. Do not make more than 3 consecutive applications of Ranman followed by at least 3 applications of fungicides having different modes of action before applying additional Ranman. Depending on the use rate, a 1 qt container will cover approximately 12 to 15 acres of vineyard with a single application. 12 hour REI, 30 day PHI.

Revus Fungicide (mandipropamid), EPA# 100-1254, READ THE LABEL

Revus provides excellent control of downy mildew with protectant, some post-infection, and perhaps some antisporulant activity, with moderate risk of disease resistance development. Revus is a new fungicide for use in grapes, and should be used in a rotational program with other downy mildew fungicides. Apply at 8 fl oz per acre per application, and no more than 32 fl oz per acre per season. Make no more than 2 consecutive applications before switching to another effective downy mildew fungicide. If applied at the recommended use rate of 8 fl oz per acre, a 1 gallon container will cover 16 acres of vineyard with a single application. 4 hour REI, 14 day PHI.

Ridomil Gold MZ WG (mefanoxam + mancozeb), EPA# 100-1269, READ THE LABEL

Ridomil Gold MZ contains two unrelated active ingredients, mefanoxam and mancozeb, with a high risk of disease resistance development. Mefanoxam provides excellent activity against downy mildew with protectant, post-infection, and antisporulant activity. Mancozeb is included in Ridomil Gold MZ to decrease the likelihood of downy mildew resistance development. Apply Ridomil Gold MZ at 2.5 lb per acre per application, and no more than 10 lb per acre per season, but the use of no more than 2 applications of any Ridomil products is highly recommended in order to decrease the risk of developing disease resistance. Ridomil Gold MZ contains the equivalent of 2 lb per acre of 75 DF mancozeb products. If black rot and Phomopsis control are desired, supplement with additional mancozeb up to the maximum amount permitted per application (add up to 2 additional lb of 75DF mancozeb or equivalent). When applied at its recommended use rate of 2.5 lb per acre, a 5 lb bag of Ridomil Gold MZ will cover 2 acres of vineyard with a single application. 48 hour REI, 66 day PHI.

Microthiol Disperss (sulfur), EPA#70506-187, READ THE LABEL

Sulfur provides protectant, post-infection, anti-sporulant, and some eradicant control of powdery mildew, with low risk of disease development, and is OMRI listed. Apply 3 to 10 lb per acre (application rates of 4 to 5 lb are typical, but higher rates can provide longer control). Some cultivars may be injured by sulfur applications, consult information in the “Grapevine Variety Characteristics Chart” or university pest management guidelines for varietal sensitivity to sulfur. Sulfur injury may be greater when air temperatures are above 85-90°F at the time of application. Tank mixing sulfur with other powdery mildew fungicides is a sound disease resistance management strategy. When applied at its recommended application rate of 3 to 10 lb per acre, a 30 lb bag of Microthiol Disperss will cover 3 to 10 acres of vineyard with a single application and can be applied every 7 to 14 days as needed, but applications near harvest should be avoided to avoid sulfur odors in finished wine. 24 hour REI, 0 day PHI.

JMS Stylet Oil (paraffinic oil), EPA# 65564-1, READ THE LABEL

JMS Stylet Oil provides post-infection, antisporulant, and eradicant activity, and modest protectant activity, against powdery mildew, with low risk of disease resistance development. Use in a 1 to 2% solution, and do not concentrate beyond 2% (2 gal product per 100 gallons). JMS Stylet Oil provides significant eradicant activity against existing powdery mildew infections, but thorough spray coverage is essential for effective control. Follow label precautions for use with copper hydroxide, mancozeb, and Ridomil. Do not tank mix with spreader stickers or certain highly ionized nutrient spray materials. Do not use captan with or following an oil spray. Do not use copper and oil together when fruit is present. Do not apply sulfur within 10 days of an oil spray. 4 hour REI, 0 day PHI.

Nutrol (potassium dihydrogen phosphate), EPA# 70644-1, READ THE LABEL

Nutrol provides post-infection, antisporulant, and limited eradicant control of powdery mildew, with low risk of disease resistance development. It provides no protective activity, but significant post-infection activity when applied within a week after the start of an infection. Apply 5-10 lb per acre per application, using a maximum 3 lb product per 10 gal. Nutrol is relatively ineffective at eradicating well-established powdery mildew infections. It is most effective when applied with short (7-day) intervals when applied sequentially, and can be used in a tank mix with other powdery mildew fungicides. For best results, apply with a non-ionic surfactant such as Induce. When applied at its recommended use rate, a 50 lb bag of Nutrol will cover 5 to 10 acres of vineyard with a single application. 4 hour REI, 0 day PHI.

Phostrol Agricultural Fungicide (phosphorous acid), EPA#55146-83, READ THE LABEL

Phostrol provides moderate protectant, post-infection, and antisporulant control of downy mildew, with moderate risk of resistance development. Apply at 2.5 to 5 pt per acre per application. Protective activity against infections is limited to 3 to 5 days after application, with significant post-infection and antisporulant activity; spray intervals should not exceed 10 days during periods of wet weather. Downy mildew resistance is known to occur in many growing regions. Do not apply Phostrol in more than 2 consecutive applications before rotating with another downy mildew fungicide, and do not apply more than 4 times per season. Some varieties are susceptible to leaf burn, test for sensitivity prior to use. When applied at its recommended use rate of 2.5 to 5 pt per acre, a 2.5 gal container of Phostrol will cover 4 to 8 acres of vineyard with a single application. 4 hour REI, 0 day PHI.

Champ Formula 2 Flowable (copper hydroxide), EPA# 55146-64, READ THE LABEL

Copper fungicides provide good activity against downy mildew, some activity against powdery mildew (but should not be relied upon for powdery mildew control on susceptible varieties), and only moderate control of black rot, with low risk of disease resistance development. Apply at 1.33 to 2.66 pt Champ Formula 2 Flowable per acre per application, do not apply more than 55 pints per acre per season. Slight to severe foliar injury may occur in copper-sensitive varieties, use the lower rate of this product and test for copper sensitivity when treating copper sensitive varieties. Hydrated lime may be added at 0.5 lb per 100 gal of spray solution to decrease the severity of phytotoxicity. Consult university spray guidelines for varietal sensitivity to copper. Slow drying conditions (cool or humid) may increase copper sensitivity; apply when foliage is dry and drying conditions are good. When applied at its recommended use rate of 1.33 to 2.66 pt per acre, a 2.5 gal container of Champ Formula 2 will cover 7.5 to 15 acres of vineyard with a single application. 48 hour REI, 0 day PHI.

DuPont Kocide 3000 Dry Flowable 10 lbs (copper hydroxide), EPA#352-662, READ THE LABEL

DuPont Kocide 3000 Dry Flowable 4 lbs (copper hydroxide), EPA#352-662, READ THE LABEL

Copper fungicides provide good activity against downy mildew, some activity against powdery mildew (but should not be relied upon for powdery mildew control on susceptible varieties), and only moderate control of black rot, with low risk of disease resistance development. Apply at 0.75-1.75 lb Kocide 3000 per acre per application, do not apply more than 66.7 lb per season. Foliar injury may result on copper sensitive varieties, either test for sensitivity or add 1 to 3 lb hydrated lime per pound of product to decrease the severity of phytotoxicity. Slight to severe foliar injury may occur in copper-sensitive varieties, use the lower rate of this product and test for copper sensitivity when treating copper sensitive varieties. Consult university pest management guidelines for varietal sensitivity to copper. Slow drying conditions (cool or humid) may increase copper sensitivity; apply when foliage is dry and drying conditions are good. When applied at its recommended use rate of 0.75 to 1.75 lb per acre, a 4 lb bag will cover approximately 2 ¼ to 5 1/3 acres of vineyard with a single application, and a 10 lb bag will cover 5.7 to 13.3 acres in a single application. 48 hour REI, 0 day PHI.

Elevate 50WDG Fungicide (fenhexamid), EPA# 66330-35, READ THE LABEL

Elevate provides very effective control of Botrytis. Apply at 1 lb per acre per application, do not make more than 2 consecutive applications, and do not apply more than 3 lb product per acre per season. Like most Botrytis fungicides, Elevate is prone to developing disease resistance. For best results, use Elevate in a rotational program with other Botrytis-specific fungicides, and limit applications to 2 or (preferably) 1 application per season to avoid the development of disease resistant strains of Botrytis. When applied at its recommended use rate of 1 lb per acre, a 2 lb bag will cover 2 acres of vineyard with a single application. 12 hour REI, 0 day PHI.

Rovral Brand 4 Flowable Fungicide (iprodione), EPA# 264-482, READ THE LABEL

Rovral provides effective control of Botrytis with protectant, post-infection, and antisporulant activity, but like most Botrytis fungicides, it is very prone to developing disease resistance. Apply Rovral at 1 to 2 pt per acre per application during early to mid-bloom, and 1.5 to 2 pt later in the season. Four applications per season are permitted on the label, but the use of only one application of Rovral per season is highly recommended, as is the use of at least one application of another effective Botrytis fungicide. When applied at the recommended use rate of 1 to 2 pt per acre, a 1 gal container of Rovral will cover 10 to 20 acres of vineyard with a single application. 48 hour REI, 7 day PHI.

Vangard WG Fungicide (cyprodinil), EPA# 100-828, READ THE LABEL

Vangard provides effective control of Botrytis with protectant, post-infection, and antisporulant activity, but like most Botrytis fungicides, is prone to developing disease resistance. Apply Vangard at 10 oz per acre per application. 3 applications per season are permitted on the label, but the use of no more than 2 applications per season are highly recommended in a rotational program with other effective and unrelated botrytis fungicides. When applied at its recommended use rate of 10 oz per acre, a 50 oz container of Vangard will cover 5 acres of vineyard with a single application. 12 hour REI, 7 day PHI.

SAMPLE DISEASE MANAGEMENT PROGRAMS FOR VINEYARDS

Vineyard disease management programs are based on several factors including variety, location, climate, seasonal weather conditions, prior disease history, and grower tolerance for risk. While it is impossible to suggest a spray program in advance of seasonal conditions for any given location, we can offer some guidance by providing examples of successful spray programs that we have used in the past. The following SAMPLE disease management programs are based on those used in our vineyards in recent years for Concord, Vidal, and Pinot Gris. Once again, we must stress that these are SAMPLE spray programs that are included in this article to illustrate successful disease management programs used in our vineyards, and they are not intended as recommended spray programs under any circumstances.

Target pests include Phomopsis (PH), black rot (BR), downy mildew (DM), powdery mildew (PM), Botrytis (BOT)

Sample disease management program for Concord

Sample disease management program for Vidal

Sample disease management program for Pinot Gris

 

INSECTICIDES

Insecticide efficacy in controlling grape insects is listed in the following table:

Insecticide Chart

Assail 30SG Insecticide (acetamiprid), EPA# 8033-36-70506, READ THE LABEL

Assail controls many insects including leafhoppers, grape berry moth, mealybug, grape phylloxera (aerial form only), banded grape bug, rose chafer, and Japanese beetle. Apply at 2.5 to 5.3 fl oz per acre per application. Begin applications when treatment thresholds have been reached. Do not make more than 2 applications per season, do not apply more than once every 14 days, and do not use spray adjuvants. When used at its recommended use rate of 2.5 to 5.3 fl. oz. per acre, a 1 quart container of Assail will cover 6 to 12.8 acres of vineyard with a single application. 12 hour REI, 3 day PHI.

Delegate WG (spinetoram), EPA# 62719-541, READ THE LABEL

Delegate controls several insects including cutworm, grape berry moth, and thrips. Apply at 3 to 5 oz per acre per application, but do not make more than 5 applications per calendar year and do not apply more than 19.5 ounces per acre per year. Do not make more than 2 consecutive applications, if additional treatments are required rotate to another class of effective insecticide for at least one application. When used at its recommended use rate of 3 to 5 ounces per acre, a 26 oz. container of Delegate will cover 6.4 to 8.7 acres of vineyard with a single application. 4 hour REI, 7 day PHI.

Drexel Carbaryl 4L(carbaryl), EPA# 19713-49, READ THE LABEL

Carbaryl is a broad-spectrum insecticide that provides control of many insect including Japanese beetle, grape leafhopper, grape berry moth, climbing cutworms, grape flea beetle, rose chafer, and other insects. Apply 1 to 2 qt per acre per application, consult the label for rate recommendations. Up to 5 applications per season are permitted with a minimum of 7 days between applications. Begin application when insect populations reach recognized economic threshold levels. Consult cooperative extension service, consultants or other qualified authorities to determine appropriate threshold levels and timing for treatment in your area. When used at its recommended use rate of 1 to 2 qt per acre, a 2.5 gallon container of Carbaryl will cover 5 to 10 acres of vineyard with a single application. 48 hour REI, 7 day PHI.

Movento (spirotetramat), EPA# 264-1050, READ THE LABEL

Movento is a systemic insecticide that controls mealybugs, phylloxera, and whiteflies, and suppresses nematodes. Apply 6 to 8 fl oz per acre per application and a maximum of 12.5 fl oz per acre per season; the minimum interval between applications is 30 days. The label recommends the addition of a spreading-penetrating adjuvant (such as Sure-Spred HV); the use of Induce adjuvant is prohibited when fruit is present. When used at its recommended use rate of 6 to 8 fl oz per acre, a 1 quart container of Movento will cover 4 to 5.3 acres of vineyard with a single application. 24 hour REI, 7 day PHI.

M-Pede (insecticidal soap), EPA# 62719-515, READ THE LABEL

M-Pede controls or suppresses some insects such as leafhoppers, mealybugs, and some mite species. Apply at 1 to 2% v/v solution (for example, 1 to 2 gal. M-Pede in 100 gal of spray solution). Apply to wet and minimize runoff as excessive water volumes will increase the potential for fruit injury. To reduce the potential for fruit injury, do not apply in greater than 75 gallons of water per acre on table grapes after berries are 6 to 7 mm in diameter. 12 hour REI, 0 day PHI.

 

HERBICIDES

Herbicide Chart

Weeds can compete with grapevines for water and nutrients resulting in reduced vine capacity. Chemical herbicides can be used to minimize weed competition in vineyards, but it is imperative that herbicide label restrictions and precautions be observed in order to avoid injury or damage to vines. Prevention is Better than Cure – Minimizing Herbicide Drift in the Vineyard describes the potential for herbicide injury in vineyards and how to avoid it by following product labels and by reducing herbicide drift through proper nozzle selection and the use of shielded herbicide applicators.

Herbicides used to control vineyard weeds are listed in the following table:

Bonide Kleen Up Weed & Grass Killer (glyphosate), EPA#4-484, READ THE LABEL

Kleen Up is a glyphosate product for use in home gardens, including grapes. Consult the label for specific recommendations.

Mad Dog Plus (glyphosate), EPA# 34704-890, READ THE LABEL

Mad Dog Plus contains 4 lb per gallon of the active ingredient glyphosate, in the form of its isopropylamine salt. Mad Dog Plus provides post-emergence, systemic control of most annual and perennial weeds in bearing and nonbearing vineyards where contact with green grape foliage can be avoided. Glyphosate is primarily absorbed through mature leaves, and it moves systemically through the plant to other plant parts including the roots, and can cause serious injury to grapevines if applied in that manner. Consult the label to determine the proper use rate for specific situations including weed species present, growth stage, and environmental factors. A maximum of 10.6 qt Mad Dog Plus, including the equivalent amount of other glyphosate products, can be applied per acre per season. Mad Dog Plus can be tank mixed with certain pre-emergence herbicides registered for use in grapes when following all product label restrictions – consult the label for a list of permissible tank mix partners. 4 hour REI, 14 day PHI.

Interline (glufosinate), EPA# 34704-1080 READ THE LABEL

Interline contains 2.34 pounds of the active ingredient glufosinate-ammonium per gallon. It is a non-selective, post-emergence herbicide used primarily in LibertyLink cropping systems, and is also registered for use in grape. Unlike glyphosate herbicides, Interline is a contact, burndown herbicide that is not translocated to underground plant parts, so is a useful alternative to glyphosate for late spring and summer applications when glyphosate contact with foliage must be avoided to minimize the risk of injury or damage to grapevines. For best results, apply to emerged, young, actively growing weeds. Warm temperatures, high humidity, and bright sunlight improve the performance of Interline. Avoid direct spray or drift to desirable vegetation. Avoid contact of spray, drift, or mist with green bark, stems, or foliage, as injury may occur. Interline is labeled for grapevine sucker control when applied to suckers 12” long or less. For sucker control, make two applications about 4 weeks apart at 56 fl. oz. per acre sprayed. Thorough coverage is needed for good control. For weed control, apply 48 to 82 fl. oz. per acre depending on weed height – consult the label for specific recommendations. Do not apply more than 246 fl. oz. Forfeit 280 per year in grapes (a maximum of 3 applications at the 82 fl. oz. rate are permitted). Directed applications made with a backpack sprayer should be made at 1.7fl. oz. Interline per gal. of water. Observe personal protective requirements on the label including coveralls, chemical resistant gloves and footwear, and protective eyewear. 12 hour REI, 14 day PHI. Not for use in Nassau and Suffolk Counties in New York.

Tuscany Herbicide (flumioxazin), EPA# 71368-102, READ THE LABEL

Tuscany provides pre-emergence, residual control of most annual broadleaf weeds and grasses. Apply 6 to 12 ounces per acre surface sprayed per application (for example, when spraying a 3’ band in 9’ rows, one acre surface sprayed equals 3 acres of vineyard). Two applications per season are allowed up to 24 ounces per acre per season, but sequential applications must be at least 30 days apart. Consult the label for restrictions for use on vines less than 3 years of age. Avoid spray contact to foliage and green bark, with the exception of undesirable suckers. Applications made after bud break require shielded applications. Tuscany provides some post-emergence activity on many weeds and grapevine suckers, however, it should be tank mixed with a labeled post-emergence herbicide for control of emerged weeds. Tuscany can be tank mixed with other pre- and post-emergence herbicides registered for use in grapes when following all product label restrictions. 12 hour reentry interval, 60 days to harvest.

Diuron 4L (diuron), EPA# 66222-54, READ THE LABEL

Diuron provides pre-emergence, residual control of many annual broadleaf weeds and grasses in established vineyards. Apply as a band treatment to established vineyards at least 3 years old. Do not apply more than 4 qt per acre surface sprayed per application with a maximum of 2 applications per year. Consult the label for additional restrictions for use on soils low in clay or organic matter. Sequential treatments must be applied at least 90 days apart. Diuron can be tank mixed with other pre- and post-emergence herbicides registered for use in grapes when following all product label restrictions. When used at its maximum use rate of 4 qt per acre, a 2.5 gallon container of Diuron 4L will cover 2.5 acres of land surface sprayed, or 7.5 acres of vineyard when a 3’ spray band is applied in a vineyard with 9’ row spacing. 12 hour REI, 0 day PHI.

Karmex DF (diuron), EPA# 66222-51, READ THE LABEL

Karmex contains the active ingredient diuron, and provides pre-emergence, residual control of many annual broadleaf weeds and grasses in established vineyards. Apply as a band treatment to established vineyards at least 3 years old. Do not apply more than 5 pounds per acre surface sprayed per application with a maximum of 2 applications per year. Consult the label for additional restrictions for use on soils low in clay or organic matter. Sequential treatments must be applied at least 90 days apart. Parrot can be tank mixed with other pre- and post-emergence herbicides registered for use in grapes when following all product label restrictions. 12 hour reentry interval, 0 days to harvest.

Drexel Simazine 4L Herbicide (simazine), EPA# 19713-060, READ THE LABEL

Simazine provides pre-emergence, residual control of annual broadleaf weeds, and early season control of annual grasses, in established vineyards. Apply 2 to 4 qt per acre surface sprayed per calendar year. Do not apply more than once per calendar year. Do not use in vineyards established less than 3 years or crop injury may occur. Simazine can be tank mixed with other pre- and post-emergence herbicides registered for use in grapes when following all product label restrictions. When used at its maximum use rate of 4 qt per acre, a 2.5 gallon container of Simazine 4L will cover 2.5 acres of land surface sprayed, or 7.5 acres of vineyard when a 3’ spray band is applied in a vineyard with 9’ row spacing. 12 hour REI, 0 day PHI.

Drexel Simazine 90 DF (simazine), EPA# 35915-12-60063, READ THE LABEL

Simazine provides pre-emergence, residual control of annual broadleaf weeds, and early season control of annual grasses, in established vineyards. Apply 2.2 to 4.4 lb per acre surface sprayed per calendar year. Do not apply more than twice per calendar year and do not apply more than 4.4 lb per calendar year. Do not use in vineyards established less than 3 years or crop injury may occur. Simazine can be tank mixed with other pre- and post-emergence herbicides registered for use in grapes when following all product label restrictions. When used at its maximum use rate of 4.4 lb per acre, a 10 lb. bag of Drexel Simazine 90 DF will cover approximately 2 ¼ acres of land surface sprayed, or approximately 6.8 acres of vineyard when a 3’ spray band is applied in a vineyard with 9’ row spacing. 12 hour REI, 0 day PHI.

Prowl H20 Herbicide (pendimethalin), EPA # 241-418, READ THE LABEL

Prowl H20 provides pre-emergence, residual control of annual grasses, and control or suppression of some annual broadleaf weeds in bearing and non-bearing vineyards. Apply 3.2 to 6.3 qt per acre surface sprayed, either in a single application or sequentially with an interval of 30 days or more, with a maximum of 6.3 qt per acre surface sprayed per season. For newly transplanted and one year grapevines, apply only when vines are dormant. Prowl H20 can be tank mixed with other pre- and post-emergence herbicides registered for use in grapes when following all product label restrictions. When applied at a rate of 6 qt per acre, a 2.5 gallon container of Prowl H20 will cover 1 2/3 acre of land surface sprayed, or 5 acres of vineyard when a 3’ spray band is applied in a vineyard with 9’ row spacing. 24 hour REI, 90 day PHI.

Solicam DF (norflurazon), EPA# 100-849, READ THE LABEL

SOLICAM IS NOT REGISTERED FOR USE IN NASSAU AND SUFFOLK COUNTIES IN NEW YORK STATE

Solicam provides pre-emergence, residual control of annual grasses, suppression of perennial grasses, and control or suppression of some annual broadleaf weeds in established vineyards. Apply 1.25 to 5 lb per acre surface sprayed, depending on soil type; consult the label for specific recommendations. Multiple or sequential applications can be made, but the total quantity of Solicam applied during a year must not exceed the maximum recommended rate for the soil type. Solicam can be tank mixed with other pre- and post-emergence herbicides registered for use in grapes when following all product label restrictions. 12 hour REI, 60 day PHI.

Surflan AS Agricultural Herbicide (oryzalin), EPA# 70506-43, READ THE LABEL

Surflan provides pre-emergence, residual control of annual grasses and some control or suppression of some annual broadleaf weeds in bearing and nonbearing vineyards. Apply 2 to 6 qt per acre surface sprayed per application, depending on the length of weed control desired. Multiple applications are allowed per season, with a minimum of 2.5 months between applications, not to exceed 12 qt per acre per year. Do not use on soils containing more than 5% organic matter. Do not apply to newly planted vines until soil has settled. Surflan can be tank mixed with other pre- and post-emergence herbicides registered for use in grapes when following all product label restrictions. When applied at its maximum use rate of 6 qt per acre, a 2.5 gal container of Surflan AS will cover 1 2/3 acre of land surface sprayed, or 5 acres of vineyard when a 3’ spray band is applied in a vineyard with 9’ row spacing. 24 hour REI, 0 day PHI.

]]> Disease Management Programs for Grapes – Part 2 https://doubleavineyards.com/news/disease-management-programs-for-grapes-part-2/ https://doubleavineyards.com/news/disease-management-programs-for-grapes-part-2/#comments Tue, 05 Apr 2016 16:00:06 +0000 https://doubleavineyards.com/blog/?p=58 Rick Dunst, Viticulturist, Double A Vineyards, Inc.

Part I provided an introduction to the major diseases that affect grapes and some options for early season disease control in vineyards. Please refer to that article for links to fact sheets for five major grape diseases – anthracnose, Phomopsis, black rot, downy mildew, and powdery mildew.

This article will focus on disease management considerations from bloom until harvest. Once again, I will rely on some of the excellent information developed for commercial grape growers through the Land Grant University system in the United States, including:

There are many other excellent resources available with information tailored to state and regional conditions. Serious grape growers should use these resources to develop an effective grape pest management program.

Most fungicides provide protection from the initiation of disease infections rather than eradication of existing infections. There are a few fungicides that provide limited eradication of existing disease infections, but essentially no fungicide has the capacity to “clean up” a raging case of disease. Because most fungicides act in a “protective” mode, they need to be applied to susceptible plant tissue PRIOR to environmental conditions that are conducive to disease development (and specific to each disease). These conditions include temperature, rainfall, hours of leaf wetness and/or humidity. As discussed in the previous article, a basic pre-bloom spray program for grapes includes a fungicide such as mancozeb (or captan or ziram) for control of Phomopsis, black rot, and downy mildew. Powdery mildew is not controlled with any of these materials, so additional fungicides are needed in an integrated spray program. There is wide variation in varietal susceptibility to powdery mildew. A complicating factor is that the powdery mildew fungus is prone to the development of resistant strains to specific fungicides after repeated applications. For this reason, effective spray programs for powdery mildew use two or more different fungicide classes on a rotational basis to prevent or delay the onset of the development of fungicide-resistant strains of powdery mildew. Fungicides with post-infection activity against powdery mildew are often tank-mixed with protective fungicides, especially during periods of high disease pressure and when grapevine tissue is most susceptible to disease.

DISEASE CONCERNS FROM BLOOM UNTIL HARVEST

Varietal susceptibility to diseases and local environmental conditions play a large role in determining a basic grape pest management spray program. For example, in western New York, a commercial ‘Concord’ grower may spray four times (more or less) for acceptable disease control, but a vinifera grower will often spray 10-12 times or more to obtain control of all major fungal diseases. Grape variety disease susceptibility ratings can be found in our “Grapevine Variety Characteristics Chart” and in university-published pest control guidelines.

Phomopsis is primarily an early season disease, with most infections occurring before and soon after bloom. Inclusion of mancozeb (NOTE: mancozeb products have a 66 day pre-harvest interval (PHI), and cannot be legally used after that time), captan, or ziram in cover sprays applied through the second post-bloom spray should be sufficient for control of Phomopsis under most conditions. Some of the strobilurin fungicides (Abound®, Sovran®, Pristine®) also provide control.

Black rot is another relatively early season disease, but primary infections that occur on leaves pre- and early post-bloom can spread to the fruit until mid-summer. Mancozeb and ziram provide good control; captan is somewhat less effective. Some of the Sterol Inhibitor (SI) fungicides including tebuconazole, Rally®, Mettle®, and Revus Top® provide effective control. Strobilurin fungicides such as Abound®, Sovran®, and Pristine® also provide effective black rot control.

Downy mildew infections can occur during the season as early as two to three weeks pre-bloom, and have the potential to “explode” under warm, wet, humid conditions. This scenario can result in premature defoliation of vines that can lead to poor fruit quality and reduced winter hardiness. Mancozeb (66 day PHI) and captan (up to 14 day PHI depending on the product label) provide effective control; ziram (14 day PHI) is somewhat less effective. Some of the strobilurin fungicides (Abound® and Pristine®) also provide effective control (Sovran®, less so). Other chemistries that provide effective control of downy mildew include, Revus® and Revus Top®, Ranman® and Ridomil®. Ridomil® is highly effective in controlling downy mildew, but is also at very high risk of developing disease resistance and should be used sparingly (i.e. no more than one application per season) under severe disease pressure. Copper fungicides can provide effective control of downy mildew, but some grape varieties are sensitive to injury (consult University guidelines and product labels to determine varietal copper sensitivity). Phosphorous acid (PA) products such as Phostrol® provide mainly post-infection control of downy mildew, but are prone to resistance development if overused.

Mancozeb, captan, ziram and copper have been used for decades and are at low risk for developing disease resistance. Fungicides that have been developed more recently usually work by interfering with a single process in fungal metabolism, typically a specific site of one specific fungal enzyme involved in the process. Hence, newly developed fungicides are almost always more prone to disease resistance development than are older ones. Wayne Wilcox discusses fungicide resistance beginning on page 10 of “2017 & 2018 Grape Disease Control”.

.

The number of pesticide applications aimed at controlling downy mildew is highly variable and depends on varietal susceptibility, weather conditions, and the amount of inoculum present in the vineyard. Like most efforts at disease control, prevention is the best medicine. The downy mildew fungus becomes active at about 10” shoot growth and infections occur with 0.1” rainfall and temperatures above 50°F. Pesticide applications aimed at controlling downy mildew on susceptible varieties should begin at about 10” shoot growth if wet conditions are anticipated. Young foliage is particularly susceptible, so several pesticide applications at 7 to 10 day intervals prior to bloom and 10 to 14 days after bloom, until about 4 weeks post-bloom, may be necessary to minimize primary infections. Once primary infections have occurred, secondary infections can occur within 4 or 5 days when there is high relative humidity at night. Disease pressure is increased with repeated humid nights, frequent rainfall, and cloudy weather. Under these conditions, downy mildew infections can explode and lead to early defoliation of vines. On susceptible varieties, once primary infections become established, a downy mildew fungicide may need to be included in spray applications every two weeks or so until early fall.

Powdery mildew infections can occur throughout the growing season, but some varieties (such as most vinifera) are much more susceptible to infections than others (such as Concord and certain other native and hybrid varieties). The powdery mildew fungus overwinters in fruiting bodies in the bark of grapevines. Spores produced from these fruiting bodies produce primary infections, and then secondary infections occur from spores released from the primary infections. Under ideal conditions (temperatures in the mid-60s to mid-80s Fahrenheit and high relative humidity), a new generation can be produced every 5-7 days. Similar to downy mildew, powdery mildew infections can explode in a short period of time and can infect leaves, clusters, and young berries.

There are five distinct classes of synthetic powdery mildew fungicides registered for use in grape in the United States:

1) Sterol Inhibitor (SI) or DMI fungicides, including tebuconazole, Rally®, Revus Top®, and Mettle®.
2) Strobilurin fungicides such as Abound®, Pristine®, Flint® and Sovran®.

3) Quintec® (quinoxyfen).
4) Vivando® (metrafenone).
5) Endura® (boscalid – typically used as one component of Pristine®).

Typically, two or more of these chemistries are used on a rotational basis by commercial grape growers, since repeated applications of the same product or products within the same chemical family can lead to the development of powdery mildew resistant strains. There are several factors that need to be considered when developing an effective powdery mildew spray program for grapes, including:

1) Phytotoxicity to certain varieties and other species – Abound® is phytotoxic to certain apple varieties; Revus Top®, Pristine®, and Flint® are phytotoxic to certain grape varieties (but not necessarily the same ones).

2) Effectiveness on other diseases – some SI fungicides (tebuconazole, Rally®, Revus Top®, Mettle®) are effective in controlling black rot, others are not. Abound® is more effective than Sovran® in controlling downy mildew; Sovran® is more effective than Abound® in controlling powdery mildew.

Consult University guidelines and pesticide labels for use guidelines and restrictions. I’ll say it one more time – “the label is the law” and the user is responsible for applying pesticides in accordance with the label.

There are also a few fungicides that provide post-infection control of powdery mildew. The powdery mildew fungus survives on the surface of grape leaves, and new infections (NOT older, established infections) can be “burned out” with topical applications of fungicides that smother or eradicate the fungus. In order for any of these fungicides to be effective in providing control of powdery mildew, they must be applied in a manner that thoroughly covers the target tissue (leaves, shoots, flower clusters, rachises, and berries).

Sulfur has been used for powdery mildew control in grapes for centuries and is not prone to resistance development, but there are cautions regarding the use of sulfur in grapes:

• Certain varieties are susceptible to sulfur injury (i.e., the cure is worse than the disease). Consult our “Grapevine Variety Characteristics Chart” or consult guidelines developed for your state or region.

• Sulfur is washed off with rainfall, so it provides little or no protection under rainy conditions. Many growers tank mix other fungicides with sulfur to obtain limited eradicant (sulfur) and protective (synthetic fungicide) activity against powdery mildew; this is recognized as a sound disease resistance management strategy.

• Late season sulfur applications may need to be avoided in order to avoid sulfur odors in finished wine.

Another fungicide that provides post-infection control of powdery mildew is JMS Stylet Oil®. If applied properly, stylet oil can eradicate powdery mildew infections from leaf surfaces by smothering it. However, there are cautions regarding the use of stylet oil in grapes including:

• Overuse can lead to reduced photosynthesis and lower sugar content in harvested grapes.

• There are incompatibility issues with several fungicides including sulfur and captan.

Once again, consult pesticide labels and University guidelines for restrictions.

A third group of fungicides that provide some post-infection control of powdery mildew includes Nutrol® (mono potassium phosphate) and other salts. These products work like “salt on a slug” and they can burn out existing infections. Salts such as Nutrol® offer post-infection (only) control of powdery mildew (only), and only on infections that are not yet visible. In contrast, stylet oil has some limited protective action, and can provide post-infection activity including once new infections become visible. However, stylet oil will not eradicate well-established colonies of powdery mildew.

While sulfur, stylet oil, and Nutrol® provide some post-infection activity against powdery mildew, they are all washed off with rainfall and must be applied often when there are rainy conditions in order to be effective. Commercial grape growers often use these products in conjunction with synthetic fungicides rather than as a substitute for them. In other words, the addition of a post-infection powdery mildew material with a protective fungicide can help control disease infections that have already occurred. This should be considered a sound disease resistance strategy when used properly in an integrated pest management program.

The number of pesticide applications needed to control powdery mildew is highly dependent upon varietal susceptibility. On vinifera and other highly susceptible cultivars, powdery mildew sprays may need to begin as early as the 3-5” shoot growth stage. Succulent foliage, flower clusters, and young berries are highly susceptible to infection, so sprays may need to be applied every 7-10 days prior to bloom, and every 10-14 days post-bloom until veraison or later. Less susceptible cultivars such as Concord may only need 3 or 4 sprays for acceptable control. The immediate pre-bloom and post-bloom sprays are the most critical for control of powdery mildew.

Botrytis and other fruit rots are the final topic of this article. A Cornell University fact sheet on Botrytis can be found at:https://ecommons.cornell.edu/bitstream/handle/1813/43080/botrytis-rot-blight-FS-NYSIPM.pdf?sequence=1&isAllowed=y .

Botrytis is a fungus that can damage blossoms, leaves, and shoots, but it is most notorious by causing bunch rot to ripening fruit. Tight-clustered varieties are most susceptible to the fruit rot phase of the disease, but infection can also occur through wounds caused by insects, hail, or fruit splitting from excessive rainfall. Infections that occur on aging flower parts can cause latent infections that become active during fruit ripening. Cultural practices that encourage air movement through the canopy can reduce disease pressure, but chemical control is often needed on susceptible varieties when there are suitable conditions for infection. All fungicides that control Botrytis are also susceptible to resistance development and should be used in a rotational program to minimize this risk. Optimal timing of applications is dependent on varietal susceptibility and weather conditions, and can include applications at late bloom, bunch close, veraison, and 2-3 weeks pre-harvest. Many grape varieties, especially those with thick-skinned berries and loose clusters, do not typically need to be sprayed for botrytis.

There are several fungicides registered for Botrytis control in grapes, including pre-packaged mixes of two fungicides, one or both active in controlling Botrytis. Consult pesticide labels and state guidelines for recommendations. Some key product groups effective in controlling Botrytis include:

1) Rovral® and generic iprodione products.
2) Vangard® and Switch® (a combination product of cyprodinil, the active ingredient in Vangard, and fludioxonil which has activity on Botrytis and certain spoilage rots.
3) Elevate®
4) Certain strobilurins including Pristine® and Flint®.
5) Endura® (one of the active ingredients in Pristine®)

Fungicides in each of these groups should not be used more than once or twice per season for Botrytis control, and should be used on a rotational basis. Captan and Pristine® have activity on certain spoilage rots (check product labels for specific recommendations). Some products have a PHI up to 14 days pre-harvest which should be considered when making late season applications.

Note that among the different groups of fungicides, only the strobilurins Pristine® and Flint® control Botrytis in addition to many of the other grape diseases. Pristine® controls Phomopsis, black rot, powdery mildew, and downy mildew, whereas Flint® controls all of those except downy mildew. Pristine® and Flint® can be used in “integrated” spray programs to control several diseases simultaneously. However, note that Pristine® and Flint® can cause injury on certain grape varieties and the pesticide labels prohibit the use of these fungicides on those varieties known to be sensitive to injury.

DEVELOPING AN INTEGRATED GRAPE DISEASE MANAGEMENT PROGRAM

Effective grape disease management programs depend on many factors including varietal sensitivity to the major diseases, weather conditions, disease susceptibility to the different groups of fungicide, the risk of fungicide toxicity to different varieties, the risk of developing resistant populations of fungi, and cost. As discussed throughout this article, there are a lot of effective fungicides available, but there are also many factors that need to be considered when developing an effective spray program.

For further information, please read Dr. Wayne Wilcox’s excellent summary article of disease management programs for grapes.

Specific guidelines for your state or region can be found online or through Cooperative Extension programs, but it is the user’s responsibility to read product labels and comply with local, state, and federal guidelines.

]]> https://doubleavineyards.com/news/disease-management-programs-for-grapes-part-2/feed/ 3 Disease Management Programs for Grapes – Part I https://doubleavineyards.com/news/disease-management-programs-for-grapes-part-i/ https://doubleavineyards.com/news/disease-management-programs-for-grapes-part-i/#comments Tue, 05 Apr 2016 15:20:32 +0000 https://doubleavineyards.com/blog/?p=56 Rick Dunst, Viticulturist, Double A Vineyards, Inc.

Managing disease is a key component to successful grape production. Cultural practices and variety selection can have a large impact on disease pressure and susceptibility, but most grape growers rely, to some extent, on chemical fungicide applications in order to produce disease-free fruit and foliage for the production of high quality fruit and wine. This article will introduce the major diseases that affect grapes, with an emphasis on cultural practices that can reduce disease inoculum in vineyards. I’ll also discuss early-season disease management from dormancy until early bloom. “Part 2” will focus on grapevine disease control from bloom through harvest.

The information included in this article is a guideline for planning an early-season pest management program for your vineyard; when using pesticides in your vineyard operation it is your responsibility to comply with local, state, and federal guidelines, and to observe label restrictions. As they say, “the label is the law”.

Many states with established grape industries publish annual pest management guidelines. University guidelines should be used to determine pesticide use appropriate for your location.

Guidelines for other states can be found online or at your local Cooperative Extension office. Remember: if you use pesticides in your vineyard operation, it is your responsibility to read the product labels and comply with local, state, and federal guidelines.

With his permission, much of the information in this article is a brief review of “2017 & 2018 Grape Disease Control” by Dr. Wayne F. Wilcox, Department of Plant Pathology, Cornell University. This article contains a wealth of information and I consider it “must read” for serious grape growers in humid regions of the United States.

Early season disease control focuses on five diseases – anthracnose, phomopsis, black rot, downy mildew, and powdery mildew. Grapevine varieties differ in their susceptibility to diseases; generally speaking, native American varieties are least susceptible, vinifera are most susceptible, and hybrid varieties are intermediate. Disease susceptibility ratings for most varieties available at Double A Vineyards can be found in our “Grapevine Variety Characteristics Chart”.

ANTHRACNOSE

Anthracnose is not a common disease in many regions, but where it occurs it can be very damaging. While there are differences in varietal susceptibility, anthracnose is more common in the warmer and more humid regions of the United States, and is most prevalent in wet years. I have never heard of a Lake Erie region Concord grower spraying for anthracnose, but it is a common practice in Concord vineyards in Arkansas. There is wide variation in varietal susceptibility. Wayne Wilcox lists Vidal, Reliance, and some other seedless cultivars as being susceptible, with some reports of disease in Concord, Catawba, and Lean Millot, more commonly in the Midwest than NY/PA. He also notes susceptibility of some of the cold hardy varieties with V. riparia in their backgroud; Marquette is particularly susceptible, other varieties mentioned include Frontenac, La Crescent, Edelweiss, Espirit, Brianna, St. Pepin, and Swenson White.

Dr. Mike Ellis at Ohio State University has published a fact sheet on anthracnose. All succulent parts of grapevines are susceptible to infection by anthracnose and Mike’s article includes several photographs to assist in identification of the disease. Several steps are recommended for management of the disease, including sanitation by pruning out infected wood and removing it from the vineyard, burying infected fruit with soil or mulch, eliminating wild grapes near the vineyard, maintaining an open canopy to improve airflow, and using fungicides. According to Wayne Wilcox, early-season sprays of mancozeb, captan, and ziram targeted against other diseases also provide significant control of anthracnose, although anthracnose is not listed on most product labels. The sterol inhibitor or DMI fungicides tend to have good activity on anthracnose, and Rally, Mettle, and Revus Top are specifically labeled for anthracnose control. Pristine is labeled for anthracnose control, but Pristine is usually saved for sprays at or after bloom. A “delayed dormant” application of lime sulfur can be very effective where anthracnose has become established; this treatment limits spore production from overwintered disease cankers but does not protect new growth from spores that are produced. As a note of caution, although lime sulfur may be considered an “organic” treatment, it is a highly caustic and corrosive material that can cause irreversible eye damage and skin burns. As with all pesticide products, users should follow precautionary statements and use personal protective equipment (PPE) described on product labels.

PHOMOPSIS

Phomopsis is a fungal pathogen that (like anthracnose) can infect all succulent tissue on grapevines if conditions are favorable. Infections that occur on the developing rachis when clusters first become visible at about 3” shoot growth are most damaging and can result in severe fruit loss. Infections at the base of green shoots weaken them and make them more susceptible to breakage, and infected wood left in the trellis can serve as a source of infection for many years. Hence, cordon-trained vines are more susceptible to disease buildup than are cane pruned vines, with hedge pruned Concord and Niagara vineyards in the Lake Erie region arguably qualifying as “poster children” for the disease.

There are several fungicides that provide effective control. Mancozeb, captan, and ziram all provide effective control of Phomopsis; these are protective materials that must be applied prior to infection. Cornell guidelines list strobilurin fungicides such and Pristine®, Abound®, Flint®, and Sovran® as providing moderate control, with copper providing only slight control. Where disease pressure is high due to weather conditions, varietal susceptibility, and training system (the presence of older, infected wood), several sprays beginning at the visible cluster stage through fruit set may be warranted.

BLACK ROT

Black rot is another fungal pathogen that thrives in warm, humid climates, and is prevalent across the eastern and midwestern United States. The disease gets started by spores blowing in from distant infections on wild grapevines, or from mummified berries from the previous year’s infections in the vineyard. Infections spread from leaves and then to fruit, and can result in complete crop loss under severe conditions. Removing “mummies” from the vineyard during pruning removes the largest source of inoculum for infection in subsequent years, and dropping mummies to the ground is better than leaving them hanging in the trellis.

Several fungicides provide effective control, including mancozeb and ziram as listed above under Phomopsis control. Captan also provides some control, but is not as effective as mancozeb and ziram. Copper only provides slight control. Cornell guidelines list strobilurin fungicides such as Pristine®, Abound®, Flint®, and Sovran® as providing excellent control, as well as some of the DMI fungicides including Revus Top®, Rally®, Mettle®, and tebuconazole. Effective sprays applied from 2-3 weeks prior to bloom to 2-3 weeks after bloom usually provide acceptable control, by limiting the seasonal inoculum harbored in the vines.

DOWNY MILDEW

Downy mildew is yet another fungal pathogen prevalent in warm, humid regions. Frequent rainfall and high humidity can promote downy mildew epidemics. Under the right conditions, downy mildew infections can “explode” and defoliate grapevines prematurely, making them more susceptible to winter injury. Primary infections occur when spores spread from leaf litter on the ground to young leaves and clusters, beginning about 2-3 weeks prior to bloom. Secondary infections occur when spores produced on leaf infections spread during nighttime periods with very high relative humidity; once the disease is established in the vineyard, secondary infections can occur late into the growing season. Practices that encourage air circulation and speed drying time can reduce disease pressure, but fungicide sprays are often needed. There is wide varietal susceptibility to downy mildew.

Fungicides that control Phomopsis and/or black rot early in the season, such as mancozeb and captan, also provide good preventative control of downy mildew. Ziram provides some control of downy mildew but is not as effective as mancozeb and captan. Copper provides good control but note that copper can cause injury to grapevine foliage, especially when leaves are succulent and downy mildew while control with Sovran® is only fair. DMI fungicides, including Rally®, Mettle®, and tebuconazole, (and also the “Top” component of Revus Top®) provide no control of downy mildew. Revus® and Revus Top® (via the mandipropamid component) provide excellent control, as does Ridomil®, and Ranman® provides good control. Ridomil® is downy mildew specific, relatively expensive, and very prone to disease resistance development, hence, Ridomil® is only labeled for use in grapes as a pre-mix with mancozeb or copper. Phosphorous acid (PA) products (such as Phostrol®) provide primarily post-infection control of downy mildew. Other than mancozeb, captan, ziram, and copper, all the fungicides listed as “effective” are prone to disease resistance development and should be used in within a sound, integrated pest management program.

POWDERY MILDEW

Powdery mildew has been described as “perhaps the most important fungal disease of grapevines worldwide” (Wayne Wilcox). Uncontrolled powdery mildew can destroy infected clusters and cause “diffuse” cluster infections that increase their susceptibility to bunch rots. Leaf infections can limit photosynthesis and reduce fruit quality, vine growth, and winter hardiness. Maintaining an open canopy that allows sunlight to penetrate into the canopy can reduce disease pressure, as can keeping vines relatively free of disease using appropriate fungicide-based disease management programs. Once established, powdery mildew infections can multiply rapidly. Rainfall is not necessary to spread the infections. Hence, early-season sprays are critical on susceptible varieties in order to avoid an epidemic. Unfortunately, fungicides that provide preventative control of Phomopsis, black rot, and downy mildew, such as mancozeb, captan, and ziram – DO NOT provide effective control of powdery mildew.

Recommendations for effective control of powdery mildew are fairly complicated, and depend on varietal susceptibility to the disease; susceptibility to phytotoxicity from sulfur and other fungicides; and, the potential to develop strains of powdery mildew that are resistant to specific fungicide chemistries following repeated use.

Varietal Susceptibility. In general, vinifera are most susceptible to powdery mildew infections, hybrids intermediate, and natives least. In Western New York, Concord growers might spray 3-4 times for powdery mildew control; hybrid growers 5-6 times; and vinifera growers 8-10 times. Growers in warmer and humid climates may spray more often than that.

Sulfur Sensitivity. Elemental sulfur can provide very effective powdery mildew control, with both preventative and curative action. Disease resistance development is not a concern. However, rainfall washes off sulfur coverage, and new shoot growth is not protected, so sulfur needs to be applied frequently in order to provide season-long control. Additionally, some grape varieties are susceptible to foliar injury from sulfur, and sulfur applications should be avoided on these varieties. Sulfur sensitivity of many varieties can be found in our “Grapevine Variety Characteristics Chart”.

Fungicides used to control powdery mildew and avoiding powdery mildew resistance. Synthetic pesticides are usually used to control powdery mildew to some extent. While some fungicides provide limited post-infection activity, they should be used primarily as protectants in order to lower the chances of developing disease resistance. These fungicides are absorbed into succulent grapevine tissue such a leaves and clusters and are generally effective for about 14 days. There are at least five distinct “families” of powdery mildew fungicides with federal registration in grapes:

1) Sterol inhibitor or “DMI” fungicides, examples include Rally®, tebuconazole, Mettle® and Revus Top®.
2) Strobilurin fungicides such as Pristine®, Abound®, Flint®, Sovran®

3) Quintec®.
4) Vivando®.
5) Endura® (typically used as one component of Pristine®)

Note: Revus Top®, Flint®, and Pristine® fungicides are phytotoxic to certain grape cultivars, and Abound® is phytotoxic to many apple varieties. Consult pesticide labels for use guidelines and restrictions.

Repeated use of any single chemistry will eventually result in resistant strains of powdery mildew that are no longer controlled with applications of fungicides within that chemistry. At least two, and preferably more of these chemistries are used in commercial grape production on a rotational basis to avoid or delay the onset of disease resistance.

As previously mentioned, elemental sulfur can be used to “burn out” previous powdery mildew infections. Another fungicide that provides post-infection control of powdery mildew is JMS Stylet Oil®. If applied properly (good spray coverage is essential for this material to be effective) stylet oil can eradicate powdery mildew infections from leaf surfaces by smothering it. However, there are cautions regarding the use of stylet oil in grapes including:

1) Overuse can lead to reduced photosynthesis and lower sugar content in harvested grapes.
2) There are incompatibility issues with several fungicides including sulfur and captan.

Once again, consult pesticide labels and University guidelines for restrictions.

A third group of fungicides that provide some post-infection control of powdery mildew includes Nutrol® (mono potassium phosphate) and other salts. These products work like “salt on a slug” and they can burn out existing infections. Salts such as Nutrol® offer post-infection (only) control of powdery mildew (only), and only on infections that are not yet visible. In contrast, stylet oil has some limited protective action, and can provide post-infection activity including once new infections become visible. However, even stylet oil will not eradicate well-established colonies of powdery mildew.

While sulfur, stylet oil, and Nutrol® provide some post-infection activity against powdery mildew and are not prone to disease resistance development, they are all washed off with rainfall and must be applied often under rainy conditions in order to be effective. Commercial grape growers often use these products in conjunction with synthetic fungicides rather than as a substitute for them. In other words, the addition of a post-infection powdery mildew material with a protective fungicide, especially at critical times when grape tissue is most susceptible, can help control disease infections that have already occurred. This should be considered a sound disease resistance strategy when used properly in an integrated pest management program.

DEVELOPING AN INTEGRATED GRAPE DISEASE MANAGEMENT PROGRAM

University researchers have developed “integrated” pest management programs that aim to provide acceptable levels of control of all the major diseases affecting grapevines. Programs are developed based on varietal susceptibility to disease and the amount of disease inoculum carried over from previous seasons. Typical pre-bloom spray programs include a fungicide such as mancozeb to provide protection against infection by Phomopsis, black rot, and downy mildew, and also one or more of the fungicides that control powdery mildew, depending on varietal susceptibility. In western New York, commercial grape growers of native varieties such as Concord often apply as few as two pre-bloom fungicide applications, while vinifera growers can apply several sprays, beginning at early shoot growth, at 7-10 day intervals.

For more specific details in developing a grape disease management program, refer to Wayne Wilcox’s summary article and your state or regional grape pest management guidelines.

]]> https://doubleavineyards.com/news/disease-management-programs-for-grapes-part-i/feed/ 3 Managing Weeds in Vineyards https://doubleavineyards.com/news/managing-weeds-in-vineyards/ https://doubleavineyards.com/news/managing-weeds-in-vineyards/#comments Thu, 28 May 2015 13:25:20 +0000 https://doubleavineyards.com/blog/?p=45  

Rick Dunst, Viticulturist, Double A Vineyards, Inc. 

 

When trouble-shooting the cause of poor growth in vineyards (especially newly-planted ones) competition from weeds is one of the first things to consider. In my experience, new growers often underestimate the competitive effects of weeds in the vineyard. This article will summarize some of the concepts of managing weeds and cover crops as well as the tools used to accomplish good weed control in vineyards.

How Competitive are Weeds and Cover Crops in Vineyards?

During my career at Cornell University’s Vineyard Research Lab in Fredonia, NY, I had the opportunity to collaborate with several excellent researchers who helped me understand the concepts of weed competition in vineyards and how to manage it. Those researchers include the late Professor Emeritus Dr. Bob Pool and Professor Emeritus Dr. Alan Lakso from the New York State Agricultural Experiment Station in Geneva, NY, and viticulturist Alice Wise and weed scientist Dr. Andy Senesac who work at the Long Island Horticultural Research and Extension Lab in Riverhead, NY. The information presented in this article is based largely on their research studies and only skims the surface of our understanding of the topics, so I have listed a few references at the conclusion of this article for those of you who might be interested in more detail.

Research at the Fredonia Lab was primarily with own-rooted Concord, a relatively shallow-rooted grapevine. Studies showed that:

  • Competition from weed or cover crop growth has a substantial effect on vine growth, and fruit yield and quality.
  • Minimizing weed competition under the vines is particularly critical on newly-planted vines.
  • Organic mulches can increase soil organic matter, conserve soil moisture, suppress weed growth, and lead to increased vine size. They can have a substantial effect on vine mineral nutrition and can result in higher potassium and lower magnesium status in grapevines.
  • Actively growing cover crops, including legumes, between bloom and veraison can reduce vine size and fruit yield.
  • Vine size and fruit yield increase proportionally to the width of the weed-free band under the vines. In one study in a mature Concord vineyard, vine growth was increased by over 300% when the entire vineyard floor was managed to exclude weed and cover crop growth, as compared with vines grown in solid sod cover, and irrigation could only minimally overcome the competitive effect of the sod.
  • Mowing a competitive cover crop such as orchard grass has only a very limited and temporary effect on reducing the competitive effect of the sod.

Concord growers typically aim to grow large crops that meet processor quality standards. Conversely, premium vinifera growers often aim for low to moderate yields in order to produce high value fruit and wine. Where high vigor varieties or rootstocks are used, vine growth can often become excessive. In the arid regions of the western United States, regulated deficit irrigation practices are often used that create moderate water deficits. These deficits can lead to improved fruit quality, especially in red cultivars. Alice Wise, Cornell viticulturist on Long Island, NY, reports that several commercial growers are successfully reducing herbicide inputs by using ground covers or mowing weeds under the vines in mature vineyards. Excessive vine growth can be tamed to some extent where vine vigor is high due to variety, heavy soil, and during heavy rainy periods. In her experience, this practice can be risky on young vines, in vineyards with light sandy soil, and during extended summer droughts, especially where supplemental irrigation is not available.

Weed Management in Vineyards

It is clear that plant growth (weeds or cover crops) under the trellis can compete excessively with grapevines for water and nutrients, limiting vine growth and fruit yield. Vineyards are primarily a hillside crop, since good air drainage and movement are needed to minimize the risk of cold damage and the development of fungal diseases. On the other hand, large areas of bare soil (especially cultivated soil) are prone to soil erosion during episodes of heavy rainfall. In most commercial vineyards in the Eastern United States, a balance between excessive weed competition and minimizing the risk of erosion is struck by maintaining a relatively weed-free band underneath the vines while maintaining green cover crops in the row middles. Typically, about one-third of the vineyard soil is maintained relatively weed-free during the summer. There are several methods to accomplish this, some more practical in smaller vineyards than in larger ones:

  • Synthetic mulches, such as plastic or geotextile, can be effective. Drawbacks include expense of the product and/or installation, and keeping the mulch in place when the wind is blowing and from equipment or foot traffic in the vineyard.
  • Organic mulches need to be applied several inches deep in order to be effective in smothering weed growth. Concerns include expense, introduction of weed seed from the use of hay, creation of habitat favorable for rodents and cutworm, and the risk of nitrogen imbalances in the vines as the organic matter decomposes.
  • Cultivating by hand as the sole means of weed control is only practical for very small vineyards. There are some effective tools for mechanical cultivation, but multiple passes are needed to maintain good weed control and it is difficult to eliminate weed growth at the base of the vines.
  • Due to the limitations and expense of these practices, chemical weed control is the most common means of weed control in commercial vineyards. Pre-emergence herbicides kill weed seedlings as they germinate. Options include Tuscany, Diuron (liquid), Diuron (dry flowable), Prowl, and Surflan. Often, two pre-emergence herbicides are tank-mixed to increase the spectrum of weeds controlled. They are also often mixed with post-emergence herbicides to kill weeds that have already emerged, in addition to providing residual control. Two or more applications of post-emergence herbicides only can also provide effective weed control in vineyards, but options are limited. Glyphosate (available in 1 gallon and 2.5 gallon containers) is a systemic herbicide that (when applied at the proper time, depending on the weed species) kills the entire weed including the roots. Glyphosate also can cause damage to grapevines if grape leaves are contacted, and the risk of damage increases as the season progresses. Forfeit is a contact “burndown” herbicide that is also registered for use in grapes, and only kills contacted tissue with no risk of translocation to other parts of the vine. Specific information on the use of herbicides in vineyards can be found here, in University pest management guidelines, and on product labels.

Weed Control in Newly-Planted Vineyards

As previously mentioned, weeds can be very competitive with newly-planted vines, to the extent that vine growth and yield can be severely compromised. Herbicide options for newly-planted vineyards include Surflan and Prowl. Glyphosate and Forfeit can be used around young vines, but again, glyphosate contact with grape leaves needs to be avoided. The use of plastic grow tubes on newly-planted vines allows multiple applications of glyphosate during the first growing season by protecting the vines from herbicide contact while minimizing weed competition during establishment of the vineyard.

References:

https://flgp.cce.cornell.edu/timeline.php?id=2

https://ecommons.cornell.edu/bitstream/handle/1813/42888/2016-org-grapes-NYSIPM.pdf?sequence=4&isAllowed=y

https://blogs.cornell.edu/nnygrapeupdate/2014/05/14/under-trellis-management-in-vineyards-part-1/

 

]]> https://doubleavineyards.com/news/managing-weeds-in-vineyards/feed/ 4 Grape Pest Management for the Homeowner https://doubleavineyards.com/news/grape-pest-management-for-the-homeowner/ https://doubleavineyards.com/news/grape-pest-management-for-the-homeowner/#comments Tue, 21 Apr 2015 21:19:57 +0000 https://doubleavineyards.com/blog/?p=23  

Rick Dunst, Viticulturist, Double A Vineyards, Inc.

 

 

Chemical pest management options for growers with only a few vines are limited. While non-restricted use pesticides can be purchased and used by anyone (meaning, anyone who reads and understands the pesticide label prior to application and applies it legally), they usually come in package sizes intended for commercial growers with at least several acres of vineyard. This article is intended for the small/homeowner/backyard/hobbyist grower producing a small amount of grapes for their personal use (or to share with friends).

While chemical control options are usually necessary in humid regions, they should not be considered the first line of offense. Grapevine varieties differ substantially in their relative resistance to disease (Grapevine Characteristics Chart), so consideration should be given to planting the least disease-susceptible cultivar that has sufficient winter hardiness to thrive at your location. Typically, vinifera cultivars are much more susceptible to grape diseases such as powdery and downy mildew, black rot, phomopsis, and in some cases, botrytis and other fruit rots, than many American and hybrid varieties. Where possible, grapevines should be planted in areas with good air movement and full-day sun to aid in drying, which will reduce the chance of disease development. We often see crop failures in wet, fenced-in backyards surrounded by trees and buildings. Finally, inoculum for some diseases can be reduced by removing infected material, such as black rot mummies or anthracnose cane lesions, from the vineyard.

There are several grapevine diseases of concern to grape growers in humid climates with spring and summer rainfall, including black rot, powdery mildew, downy mildew, phomopsis, and anthracnose. If you need assistance in determining which disease(s) are an issue in your vineyard, refer to these University fact sheets:

Fact sheet on black rot

Fact sheet on powdery mildew

Fact sheet on downy mildew

Fact sheet on phomopsis

Fact sheet on anthracnose

It is important for the grower to understand that chemical controls for grapevine diseases are usually made on a preventative basis, meaning that control measures should be taken before infection has taken place. Once you see disease infection in the vineyard, sprays can be applied to prevent or minimize future infections, but existing infections will not be eradicated, and in most cases they provide inoculum to further spread the disease during the current growing season.

Double A Vineyards offers several homeowner chemical fungicides on our website that, if used on a preventative basis at timely intervals, provide control of all five listed grapevine diseases. These products include Spectracide Immumox and several Bonide products including Captan-50% WP, Fruit Tree Spray Concentrate (a pre-mix of Captan plus insecticide), Sulfur Plant Fungicide, All Seasons Spray Oil, and Copper Fungicide. While the following information is based on information provided on product labels and on many years of experience, Double A Vineyards will not be held liable for any reason should our customers decide to use these products. It is the responsibility of the applicator to read and understand the pesticide label prior to application, and apply it in legal fashion according to local, state, and federal regulations.

Application rates for all the products listed in this article are based on an amount of product per gallon of spray mix. Sprays should be applied just prior to the point of runoff on leaves and clusters.

Spectracide Immunox (1.25 fl. oz. per gallon) + Bonide Captan-50% WP(1.5 Tbsp. per gallon) is a basic homeowner spray mix that controls anthracnose, black rot, powdery mildew, downy mildew, and phomopsis. Spectracide Immunox contains the same active ingredient, myclobutanil, as the commercial product Rally. Unlike any of the other homeowner products, it is labeled for control of anthracnose and black rot, and it also controls powdery mildew. Spectracide Immunox should be applied starting at 1-3” shoot growth and can be reapplied every 14 days up to a maximum of 5 applications per season. Sprayed at 1.25 fl. oz. per gallon, one pint container of Spectracide Immunox makes 12.8 gallons of spray mix. Captan should be added for control of downy mildew and phomopsis. Captan provides some suppression of black rot, but should not be depended upon to control the disease under high pressure. Captan can be applied at 10-14 day intervals up to the day of harvest. Do not mix Captan with or closely follow an oil spray, and do not mix Captan with highly alkaline materials such as hydrated lime. Sprayed at 1.5 Tbsp. per gallon, one 8 oz. container of Bonide Captan makes approximately 18 gallons of spray mix.

For control of insects such as flea beetle, Japanese beetle, rose chafer, grape berry moth, leafhoppers, and mealybugs, substitute Bonide Fruit Tree Spray Concentrate (1.5-2.5 Tbsp. or 0.75-1.25 fl. oz. per gallon) for Captan in the above mix, or apply as a separate spray when insects are present. Fruit Tree Spray Concentrate is a combination of Captan and two insecticides, Malathion and Carbaryl. Two applications per year are permitted with a minimum re-treatment interval of 14 days. Do not spray Fruit Tree Spray Concentrate when temperature is above 85°F nor within 7 days of harvest. Sprayed at 0.75 – 1.25 fl. oz. per gallon, one pint container makes 12.8 to 21.3 gallons of spray mix.

For increased control of powdery mildew, Bonide Sulfur Plant Fungicide (1-3 Tbsp. per gal.) can be added to any spray on sulfur-tolerant varieties in a tank mix or can be alternated with Spectracide Immunox. This is a useful spray on varieties very susceptible to powdery mildew and tolerant of sulfur applications. Sulfur can be substituted for Spectracide Immunox for control of powdery mildew, but sulfur does not control black rot. CAUSES INJURY ON SULFUR-SENSITIVE VARIETIES – consult Double A Vineyards’ Grapevine Characteristics Chart for varietal sulfur sensitivity. Applied at 1-3 Tbsp. per gallon, one 4 lb. package of Bonide Sulfur will make at least 50 gallons of spray mix.

Bonide All Seasons Spray Oil (2.5-7.5 Tbsp. or 1.25-3.75 fl. oz. per gallon) controls certain insect pests and young powdery mildew infections by smothering them. For powdery mildew control, sprays can begin before bloom and repeat every 10 days (or up to 3 weeks). Good coverage is essential for control. Under high disease conditions, such as when the disease has already begun to establish and powdery mildew colonies are visible, the label recommends use of 7.5 Tbsp. per gallon and/or shorter spray intervals. Insects including mealybug, mites, and leafhoppers can be controlled by smothering them with oil. Do not mix All Season Spray Oil with Captan and do not apply within 14 days of a Captan application. Do not mix All Season Spray Oil with sulfur nor apply when sulfur is on the foliage. Do not mix All Season Spray Oil with copper more than once per season nor when fruit is present. Do not apply All Season Spray Oil if temperature is >90°F or less than 40°F. Table grapes cannot be sprayed with All Season Spray Oil within 60 days of harvest. Oil application will remove the bloom on grape skin. Sprayed at 1.25-3.75 fl. oz. per gallon, a one-quart container of Bonide All Season Spray Oil makes 8.5 to 25.6 gallons of spray mix. Commercial growers typically spray oil in a 1.5-2% solution, or 2-2.5 fl. oz. per gallon, so a one-quart container would typically make 12.8 to 16 gallons of spray mix.

Bonide Copper Fungicide (2-26 oz. per gallon) provides control of downy mildew and suppression of black rot, powdery mildew, and phomopsis. Applications can be made throughout the season. Copper can be used as a substitute for Captan in any mix, or as a late-season spray, but copper can cause injury on many grape varieties, especially after repeated applications or under slow drying conditions. Do not mix copper with oil. Copper controls downy mildew but provides only suppression of phomopsis, black rot, and powdery mildew, so it should not be depended upon for control of these diseases under high disease pressure. CAUSES INJURY ON COPPER-SENSITIVE VARIETIES. Sprayed at 2-26 oz. per gallon, one 16 oz. container of Bonide Copper makes 0.6 to 8 gallons of spray mix.

Customers often ask how many vines can be sprayed using one or more containers of a particular product. The answer is: it depends. All of the homeowner pesticides discussed in this article are applied by mixing a rate of product per gallon of water, and application should obtain thorough coverage of leaves and clusters. The number of vines you can spray with a gallon of spray mix will depend on the time of the season and the amount of growth on the vines. Commercial growers often spray at 50 GPA (gallons per acre) for pre-bloom sprays when the canopy is not yet completely filled, while later-season sprays might require 100-200 GPA to obtain good coverage.

]]> https://doubleavineyards.com/news/grape-pest-management-for-the-homeowner/feed/ 2 How to Calibrate and Use a Backpack Sprayer https://doubleavineyards.com/news/how-to-calibrate-and-use-a-backpack-sprayer/ https://doubleavineyards.com/news/how-to-calibrate-and-use-a-backpack-sprayer/#comments Wed, 18 Mar 2015 21:20:25 +0000 https://doubleavineyards.com/blog/?p=25  

Rick Dunst, Viticulturist, Double A Vineyards, Inc.

 

 

Small vineyard owners often find that they need to spray chemicals for control of weeds, insects, and disease, but can’t justify the expense of a tractor-operated sprayer (not to mention the tractor). The need for chemical applications to control grapevine diseases can be minimized by selecting cultivars that are relatively disease-resistant, and by planting the vineyard in a location with full sunlight and good air movement. However, in humid climates, some fungicide applications are almost always needed to maintain a healthy canopy of leaves and/or disease-free fruit. Most fungicides are applied to prevent the development of diseases, while insecticides are usually applied when insects are present and have met or exceeded established thresholds. In very small vineyards weeds can be controlled by hand-pulling or hoeing, or by applying organic or synthetic mulches, but larger vineyards often require the application of chemical herbicides. Finally, wildlife predation by deer, rabbits, and birds is sometimes accomplished with the use of exclusion devices such as fences and netting, but repellant sprays are sometimes needed to minimize predatory damage to young vines or to fruit.

There are many brands of backpack sprayers on the market that are completely hand- (and foot-) powered. Double A Vineyards sells a “Deluxe” Solo brand sprayer that holds 4 gallons of water or spray mix and has a pressure gauge to ensure an even application rate. The sprayer is pressurized with a hand lever pump. While spraying, keep pressure constant by pumping down on the lever and maintaining a steady reading on the pressure gauge. The Solo Deluxe sprayer includes several nozzle types. Many standard agricultural spray tips can also be used – use whatever nozzle gives you the spray coverage you are looking for.

When making foliar applications of fungicides or insecticides to the canopy, thorough coverage of the target (leaves and/or fruit, depending on the pest to be controlled) is necessary. Canopies need to be sprayed from both sides of the row. Application instructions found on the label of the product you are using can be based on an amount of pesticide per volume of spray mix or as an amount of product to use per acre of vineyard. Examples include the following:

Some pesticides packaged for the homeowner provide instructions based on an amount of pesticide per gallon of spray mix. For example, label instructions for Bonide Captan 50WP state, “Use 1 to 1 ½ Tbs. per gal. of water. Apply sufficient spray volume to provide thorough, even coverage…. Use the lower rate when spraying less susceptible grape varieties or when conditions are less favorable for disease development. Use the higher rate on susceptible grape varieties and during periods of weather highly favorable for disease development.” In other words, mix the desired amount of product per volume of water, and apply so that all target fruit and foliage is covered, but not so much that the spray is dripping from the canopy. Another example of a pesticide that is applied as a percent solution is JMS Stylet Oil, often applied to control powdery mildew. The stylet oil label instructs, “Apply at 1-2 gal per 100 gal. water (a 1-2% solution). Spray for optimum coverage of leaf surfaces. For powdery mildew control, use the higher rate … when disease conditions are severe.” In order to achieve optimum coverage, sprays should be applied to, but not beyond, the point of runoff.

As opposed to application rates based on an amount of product per volume of water, most commercial pesticide products are labeled for application at an amount of product per acre of vineyard. This type of application will require careful sprayer calibration. Let’s use the example of Microthiol Sulfur, which is labeled at application rates ranging from 3-10 lb. per acre per application for control of powdery mildew, and you want to apply this product at a typical application rate of 5 lbs. per acre. In order to make this application correctly (and legally), you need to know how many vines there are in an acre of your vineyard, and how many vines you can spray with a given volume of spray solution. Sprayer calibration should be performed using a known volume of clean water in the sprayer. For example: your vineyard is planted at 8’ x 6’ spacing, with 908 vines per acre (determined from the table in our catalog, or by using this formula: Vines per Acre = 43,560/ (feet between rows x feet between vines. 43,560 is the number of square feet in an acre). Fill the sprayer with a known quantity of water, and spray the vines to obtain the desired coverage from both sides of the vines until the sprayer is empty to determine how many vines are sprayed (alternatively, spray the vines from one side of the row and divide the number of vines sprayed by 2). For this example, let’s assume you spray 10 vines from both sides with 1 gallons of water. Divide the number of vines per acre by the number of vines sprayed with one gallon of water to determine how many gallons of water are necessary to spray one acre of vines. In this example, 908 vines per acre / 10 vines sprayed with one gallon = 90.8 gal./acre. It will take 90.8 gallons of water to spray one acre of grapes. Since you want to spray 5 lb. sulfur per acre, mix 5 lb. (80 ounces) sulfur per 90.8 gallons, or 0.88 oz. sulfur/gal. Use a postal scale or other accurate scale to weigh the sulfur. Dilute spray volumes are usually in the range of 50 to 100 gal. per acre.

Herbicide calibration can also be based on an amount of product to be used per gallon of water or on a per acre basis (but please read the next paragraph for one important difference). Glyphosate herbicide (original trade name: Roundup) can be applied according to label instructions using an amount of product per gallon of water, with the product rate varying depending on the weed species to be controlled. Glyphosate is a systemic herbicide (meaning it is taken up by mature leaves on actively growing plants and translocated throughout the plant). Glyphosate is more effective at higher concentration, so spraying to runoff is not necessary.

Pre-emergence herbicides are applied on a per-acre basis, but an important distinction needs to be made – herbicide rates are determined on the basis of a rate PER ACRE OF LAND SPRAYED, not per acre of vineyard. To determine how many acres of land are sprayed per acre of vineyard, divide the row width by the herbicide band width. For example, if you are spraying a 32” herbicide strip in a vineyard with 8’ rows, you would spray the desired amount of herbicide on 3 acres of vineyard (96” row width / 32” band width = 3 acres of land sprayed per acre of vineyard). Using the same example vineyard used for foliar spraying (8’ x 6’ spacing)), there are 908 vines per acre. Assume you are spraying a 32” herbicide band, so you will spray 1 acre of land in 3 acres of vineyard, or 2,724 vines. For this example, let’s assume 1 gallon of water sprays 100 vines from both sides (or 200 vines from one side). 2,724 vines per acre sprayed / 100 vines sprayed with one gallon of water = 27.24 gallons per acre sprayed. Mix the amount of herbicide desired (i.e. 4 lbs. per acre in 27.24 gal/acre = 0.15 lb. or 2.35 oz./gal.). Herbicides are usually applied at 25 to 40 gal. per acre sprayed.

When applying herbicides with a backpack sprayer, I typically use a Tee-Jet 8004 flat fan nozzle. The “80” in the nozzle designation indicates the angle of spray delivered – use of a higher degree tip would require holding the nozzle closer to the ground for making a band application of herbicide, and would make applications of post-emergence herbicides such as glyphosate (Roundup) more difficult when herbicide contact with grapevine foliage needs to be avoided. The “04” indicates the volume of spray that will be delivered – a lower numbered nozzle delivers less spray volume at the same operating pressure, and a higher numbered nozzle more. In my experience using the Tee-Jet 8004 nozzle spraying herbicide in a 16” band on each side of the row, at a comfortable walking pace and 35 psi, covers 1 acre of land sprayed with 40 gallons of mix. Each operator should calibrate their sprayer at their own pace, using the selected nozzle type, size, and operating pressure.

]]> https://doubleavineyards.com/news/how-to-calibrate-and-use-a-backpack-sprayer/feed/ 1 Grapevine Red Blotch Disease https://doubleavineyards.com/news/grapevine-red-blotch-disease/ Sat, 23 Nov 2013 13:52:15 +0000 https://doubleavineyards.com/blog/?p=61 Rick Dunst, Viticulturist, Double A Vineyards, Inc. 

 

Grapevine red blotch-associated virus (GRBaV) is a recently identified virus which represents the latest addition to the long list of graft-transmissible agents that have been discovered in grapevines. This article will summarize what is currently known and not known about red blotch, and the future for the production of virus-free “cleaner” grapevines.

HISTORICAL PERSPECTIVE

In the early 1990s, vines with red leaf symptoms were observed in California and elsewhere on many selections, but they tested negative for leafroll viruses. Researchers were stumped in their efforts to determine a cause, and terms like “red leaf”, “leafroll-like”, and “false leafroll” were used to describe the disease, now known as red blotch.

In about 2007, growers in California began noticing an increase in vines with red leaf symptoms similar to symptoms of leafroll viruses, on vines planted from both certified and non-certified budwood. Over the next few years, samples from many of these vines were evaluated for viruses. Many tested negative for leafroll viruses, and attempts to find a new or variant leafroll virus (one not detected with current methodology) failed. In 2008, observations made in commercial and experimental vineyards in California and New York indicated the presence of some vines with red leaves and low sugar levels or delayed harvest. The red leaf symptoms typically began prior to veraison at the basal end of shoots, and appeared similar, but not identical, to those associated with leafroll viruses. Typically, there was no cupping or rolling of leaves as is associated with leafroll viruses, and leaf veins sometimes turned red, as opposed to the leafroll symptom of leaves turning red but retaining green veins.

In the fall of 2010, dormant canes were collected from symptomatic vines of several red vinifera cultivars. In 2011, researchers at Cornell University isolated a new virus from these canes, and researchers at the University of California discovered the identical virus. In October 2012, these researchers reported their discovery and agreed to name this new virus grapevine red blotch-associated virus (GRBaV). Detection efforts for GRBaV were initiated after that meeting, and commercial diagnostic labs now (since October 2012) have the ability to test for the disease.

EFFECTS OF RED BLOTCH ON GRAPEVINES

Red blotch is now known to occur in several red and white vinifera cultivars. Leaf reddening, starting at the basal end of shoots, is the primary symptom of red blotch on red cultivars. As previously mentioned, leaf symptoms are similar to leafroll virus symptoms. With both leafroll and red blotch, leaves turn red in late summer or early fall, primarily at the base of shoots. With leafroll, red leaves retain green veins, and leaf margins roll downward. With red blotch, leaf veins often turn red or pink, and rolling of leaf margins is absent. A side by side comparison of typical symptoms of red blotch and leafroll viruses can be found at: http://ucanr.edu/sites/NCPNGrapes/files/161782.pdf . Symptoms of red blotch can be variable, and likely depend on environmental factors, cultivar, and perhaps rootstock. In some Eastern US vineyards, typical symptoms are red blotches on leaves, but veins may remain green, or the veins may turn yellow or red (Photo 1). Leaves sometimes turn crimson red by the end of the season, and fully symptomatic leaves may dry up and prematurely drop from the vines. Red blotch has been found in some white vinifera cultivars, but symptoms are less noticeable and have been described as a slight chlorosis (yellowing) of the leaves. For the most part, vine growth and yield does not appear to be greatly impacted by the virus, but in some cases, newly planted vines that are infected with red blotch have stunted shoot growth.

Red blotch has often, but not always, been associated with lower brix or delayed harvest. In California, symptomatic vines (those expressing the red leaf symptoms described above) that test positive for GRBaV have been associated with brix levels as much as 4-5 units lower than fruit on vines with healthy green canopies at harvest. Occasionally, red blotch has been associated with poor color development and increased acidity.

WHAT WE CURRENTLY KNOW ABOUT RED BLOTCH

Red blotch is a graft-transmissible virus.

To date, vines infected with GRBaV have been identified in 20 cultivars in 8 states.

GRBaV is a DNA virus that is highly associated with symptomatic vines. In University evaluations, 96% of symptomatic vines tested positive for the virus, and 2.5% of symptomless vines contained the virus, the latter likely due to a delay in symptom development.

Symptomatic vines that have the virus are often associated with reduced brix or delayed harvest, and are sometimes associated with higher acidity at harvest. However, problems ripening fruit have not been an issue in all vineyards in which vines have tested positive for red blotch, and the severity of symptoms is not the same every year.

A PCR assay has been available for diagnosis through commercial laboratories since October 2012. Many increase blocks have been evaluated since that time and are no longer being used as a source of budwood; however, that means that until very recently, nurseries using propagation material that met current California virus certification standards have likely been producing and selling grapevines that contain the red blotch virus.

Virus elimination therapy techniques currently being used at Foundation Plant Services appear to be effective in eliminating the virus. At last report, three selections out of 1620 in the Classic Foundation Vineyard (the source of budwood for many established certified increase blocks) tested positive for GRBaV (there are about 5000 selections total in this vineyard). Additionally, all 1100 selections evaluated from the Russell Ranch vineyard have tested negative for the disease. The Russell Ranch planting is being developed through the National Clean Plant Network as the next source of certified budwood, and uses techniques such as micro shoot tip cultivation that have been effective in eliminating other known graft transmissible viruses in grapevines, with the exception of rupestris stem pitting-associated virus.

Late summer and early fall is recognized as the preferred time to sample for leafroll viruses, typically by sampling mature leaves. Recent research indicates that any grapevine tissue collected at any time is suitable for the detection of red blotch, including collection of mature leaves in late summer and early fall when red leaf symptoms develop, and also dormant canes collected in winter.

There are indications of an increased incidence over time of red blotch in some vineyards.

WHAT WE NEED TO LEARN ABOUT RED BLOTCH

First and foremost, we need to understand how red blotch is spread in vineyards, other than by propagation. In the case of leafroll viruses, we understand that the disease can be vectored by mealy bugs. In the case of red blotch, it appears that the incidence of the disease is increasing in some blocks, but we don’t know how quickly it is being spread, or the identity of the vector or vectors involved in the spread of the disease.

While researchers have found that red blotch can be detected by sampling any grapevine tissue at any time, further research needs to be performed to determine the optimal time and tissue for sampling.

While the presence of GRBaV has been associated with lower brix or delayed harvest and other potential wine quality issues, this is not always the case. Many wineries in California are producing separate lots of wine from the 2013 harvest from red blotch positive and negative sources, so we should begin to get a better handle on wine quality issues in the near future.

All vineyard blocks contaminated with red blotch do not respond in the same way. We need to understand differences due to site, management practices, cultivar selection, and variety/rootstock interactions.

WHERE DO WE GO FROM HERE?

Until just over a year ago (October 2012) there was no test available for red blotch. Since then, all of Double A Vineyard’s sources of vinifera budwood have been sampled and evaluated for the presence of GRBaV, and we have discontinued collecting propagation material (budwood and rootstock) from all blocks in which the virus has been found. Moving forward, we anticipate very low if any incidence of red blotch in our nursery stock. However, we cannot guarantee 100% freedom from red blotch in our vines at this time for the following reasons: not every vine has been sampled, false negatives are known to occur in testing for grapevine viruses, and additional red blotch infections may occur in vineyard blocks that previously tested free of GRBaV. The likelihood of the latter will be better understood once we identify the vector or vectors responsible for transmitting the disease.

Moving forward, Double A Vineyards is committed to developing new propagation blocks from plant material obtained through the National Clean Plant Network (NCPN). The NCPN was founded in 2008 and has developed updated and stricter “Protocol 2010” standards that confirm the absence of many plant pathogens, including viruses, according to our current knowledge. To qualify as Protocol 2010 plant material, the vines must have been generated using microshoot tip culture and be tested for an extensive list of pathogens. This process can take several years for each selection produced. When vines are produced that meet the Protocol 2010 standards, they are planted in the primary NCPN foundation collection at Russell Ranch near Davis, California.

The first vines to qualify for Protocol 2010 vines were rootstocks, and were planted in 2011. There are now over 1000 vines planted at Russell Ranch that are starting to produce plant material for grapevine nurseries. To date, we have only been able to obtain a very limited number of relatively few selections as softwood cuttings or mist propagated plants. This winter, we plan to obtain cuttings from several selections. These will be grafted to rootstock that also meets the Protocol 2010 standards, and in 2014 we will begin to establish vines in our new increase block for a cleaner source of planting material. Increase blocks planted from Russell Ranch material will need to conform to strict standards of sanitation and frequent re-testing to ensure the vines continue to meet the Protocol 2010 standards. Double A Vineyard’s increase block represents a substantial investment and a major commitment to improving the cleanliness of the plant material we offer. Although the waiting time for plant material that meets Protocol 2010 standards has been longer than hoped for, we believe the establishment of new increase blocks from this germplasm represents the best opportunity to offer the cleanest vines available to the grape industry in the near future.

RED LEAF SYMPTOMS IN NEWLY-PLANTED VINEYARDS

As discussed in this article, viruses such as leafroll and red blotch are often associated with red leaf symptoms, especially in red cultivars. However, there are numerous other causes of red leaf symptoms in vineyards. In our experience, red leaf symptoms are often associated with environmental factors, nutritional deficiencies (particularly magnesium deficiency) and also trunk issues such as winter injury and crown gall. In 2013, some own-rooted Chambourcin vines planted in our propagation block near Fredonia, New York, exhibited red leaf symptoms and were interspersed among vines that did not exhibit similar symptoms. Samples from symptomatic (red leaf symptoms) and non-symptomatic vines were evaluated by Dr. Marc Fuchs at Cornell University, and tested negative for many viruses, including leafroll viruses and red blotch (Photo 2). Growers should not assume that red leaf symptoms are associated with a virus. This is especially true if all or almost all vines in a block exhibit symptoms, or if they are all congregated in a section of vineyard that may have different soil nutrition or moisture conditions. In most cases, viruses are not present in every vine in a given block, so the presence of virus and associated symptoms is expected to occur in random, haphazard fashion in vineyard blocks planted from budwood obtained from a contaminated source.

Many private laboratories provide diagnostic services to detect grapevine viruses including red blotch. Contact your state Extension service, farm advisor, or Double A Vineyards for a list of laboratories if you suspect virus in your vineyards and want to test for it.

REFERENCES

“Grapevine Red Blotch Disease: An Emerging Issue”. Webinar recording featuring Dr. Marc Fuchs (Cornell University), Rhonda Smith (UC Cooperative Extension, Sonoma County) and Dr. Deborah Golino (UC Davis Foundation Plant Services). March 27, 2013.
https://www.youtube.com/watch?v=pEjqpBfXvC0

“Red Blotch: Challenges and Opportunities”, a seminar by Dr. Marc Fuchs, Cornell University, presented November 14, 2013, at the UC Davis Convention Center. This is an overview of the most current information about Red Blotch disease of grapevines and the virus that causes it.

“Grapevine Red Blotch Disease” published by the National Clean Plant Network:
http://iv.ucdavis.edu/files/162288.pdf

Website for the National Clean Plant Network – Grapes:
http://ucanr.edu/sites/NCPNGrapes/About_NCPN_Grapes/

]]> Wet Weather Brings High Disease Pressure to Vineyards https://doubleavineyards.com/news/wet-weather-brings-high-disease-pressure-to-vineyards/ Fri, 26 Jul 2013 14:11:35 +0000 https://doubleavineyards.com/blog/?p=63  

Rick Dunst, Viticulturist, Double A Vineyards, Inc.

 

Higher than average precipitation across many parts of the Eastern and Midwestern states has brought disease management issues to the forefront. Over the past several weeks, our staff has been contacted by grape growers from many growing regions with disease problems in their vineyards, many which had not been seen in prior years, or at least not to the extent that they have occurred this year. We have received questions from growers about five early-season diseases, all caused by fungal pathogens: black rot, downy mildew, powdery mildew, anthracnose, and phomopsis. Inoculum for these pathogens are present in most vineyards. The combination of disease potential with high precipitation and high humidity, especially during events that lasted for an extended period of time, have resulted in high disease pressure in many vineyards this year.

BLACK ROT

Black rot is a fungal pathogen that thrives in warm, humid climates, and is prevalent across the eastern and mid-western United States. Native American and hybrid cultivars vary widely in their susceptibility to black rot, whereas all common vinifera varieties are highly susceptible.

Cornell University fact sheet on black rot

Initial black rot infections can occur from inoculum in the vineyard, or can be blown in from a distance. Infections typically spread from mummified berries from the previous year’s infections to leaves, and then to fruit, and under severe conditions can result in complete crop loss. All young green vine tissues are susceptible to infection; leaf and fruit infections are the most common. Small (0.25” or less) brown circular lesions develop on infected leaves, and within a few days, tiny (but clearly visible) black fruiting bodies called pycnidia form within the lesions. Fruit infections first appear as small light brown circular areas that spread to the entire berry within days. The berries turn darker brown with masses of black pycnidia on the surface, and then shrivel into hard black raisin-like “mummies”. These mummies, as well as cane lesions, serve as the major source of inoculum in future years, so it is important to remove them from the vineyard during winter pruning.

DOWNY MILDEW

Downy mildew is another fungal pathogen prevalent in warm, humid regions. Vinifera cultivars are most susceptible to infection by downy mildew, with wide variation of susceptibility among native American and hybrid varieties.

Cornell University fact sheet on downy mildew

Downy mildew inoculum overwinters in leaf debris on the vineyard floor. Spores are spread by rain splash to young leaves, flower clusters, and fruit. Sporulation occurs on plant tissue containing stomata, which typically results in lesions with a white “downy” appearance on the undersides of leaves or other infected tissue. In some cultivars such as ‘Concord’, leaf infections are less common, but infected berries become reddish colored, sometimes without much visible sporulation. Under the “right” conditions, downy mildew infections can “explode” and defoliate grapevines prematurely, making them more susceptible to winter injury. Vineyards with poor air circulation that extend wetting periods are most susceptible to outbreaks of downy mildew.

POWDERY MILDEW

Powdery mildew has been described as “perhaps the most important fungal disease of grapevines worldwide” (Dr. Wayne Wilcox, Cornell University). There is wide variation in varietal susceptibility to powdery mildew infection. Generally, vinifera cultivars are most susceptible and native American cultivars least susceptible, but control measures are often needed even on only moderately susceptible varieties.

Cornell University fact sheet on powdery mildew

In the Eastern United States, powdery mildew overwinters as cleistothecia within cracks in the bark of grapevines. Under certain conditions (temperatures over 50 degrees F and 0.1” rainfall), the cleistothecia discharge spores into the air. When these spores land on leaves or clusters, they germinate and form a small, inconspicuous fungal colony on the surface of infected tissue. After these primary infections have developed, additional secondary infections from spores (called conidia) are wind-blown and do not require rainfall for dispersal or infection. Hence, early-season sprays are critical on susceptible varieties in order to avoid an epidemic. Once primary infections have developed, “every day is a powdery mildew infection day”, and spread of the disease is enhanced with high relative humidity. Uncontrolled powdery mildew can destroy infected clusters and cause “diffuse” cluster infections that increase their susceptibility to bunch rots. Leaf infections can limit photosynthesis and reduce fruit quality, vine growth, and winter hardiness.

Powdery mildew infections result in a white to grayish-white “powdery” appearance on infected surfaces. Infections usually become darker-colored over time, and infected berries sometimes shrivel or crack. Powdery mildew is usually easily distinguishable from downy mildew. Powdery mildew is usually more grayish, and leaf infections occur on the top of infected leaves. Downy mildew is white, and leaf infections occur only on the bottom of infected leaves

ANTHRACNOSE

Anthracnose is not a common disease in grapes in all grape regions, but where it occurs, it can be very damaging. Anthracnose is more common in the warmer and more humid regions of the United States, and is most prevalent in years with multiple rain events early to mid-season. Cornell University guidelines list Vidal, Marquette, Frontenac, La Crescent, Reliance, and a few other seedless cultivars as being particularly susceptible to the disease. Some cold-hardy cultivars such as Edelweiss, Esprit, Brianna, St. Pepin, and Swenson White are somewhat susceptible. Anthracnose has been reported on Concord, Catawba, and Leon Millot in the Midwest, but such occurrences are rare in Northeastern states.

Dr. Mike Ellis at Ohio State University has written a fact sheet on anthracnose that can be found at: https://ohioline.osu.edu/factsheet/plpath-fru-15 .

Anthracnose overwinters on infected canes and berries, and spores are spread by raindrops to young, susceptible tissue. Additional spores are produced from these infections and are spread by rain. All succulent parts of the vine are susceptible; lesions on leaves, shoots, and berries are most common. Leaf infections appear as numerous small, circular brown spots that turn gray in the center with brown or black margins. Leaf symptoms are easily distinguishable from black rot lesions which are circular brown spots with minute black picnidia inside the lesions. Shoot infections result in dark, sunken lesions, typically at the base of the shoot. Berry infections result in small (ca. 0.25” diameter) spots, with whitish-gray centers surrounded by reddish brown to black margins (referred to as “bird’s eye” symptoms). Thus, berry infections caused by anthracnose are also distinguishable from those caused by black rot, although severe berry infections can shrivel and dry into mummies that appear similar to those caused by black rot. Removal of infected canes from the vineyard is an important aspect of controlling the spread of anthracnose in vineyards.

PHOMOPSIS

Phomopsis is a fungal pathogen that, like anthracnose, can infect all succulent tissue on grapevines (if conditions are favorable) and is common in most viticulture regions of the world.

Cornell University fact sheet on phomopsis

Phompsis overwinters in infected canes and rachises. Rainy weather during the growing season is necessary for movement of spores from overwintering infections to susceptible tissue. Leaf infections result in small, light green spots. Infections that occur on the developing rachis when clusters first become visible at about 3” shoot growth are most damaging and can result in severe fruit loss because whole clusters or cluster segments can abscise from the vines. Infections at the base of green shoots produce elongated lesions that weaken them and make them more susceptible to breakage. Rachis infections result in sunken black lesions that may girdle the rachis and cause berries below the infection to shrivel. Berries can become infected shortly after bloom, but the disease may remain latent until fruit ripening. Infected berries develop brownish coloration, and black fruiting bodies may appear on the skin of the fruit. Infected wood left in the trellis can serve as a source of infection for many years. Hence, cordon trained vines, especially those that are hedge-pruned, are more susceptible to disease buildup than are cane-pruned vines.

MANAGING GRAPEVINE DISEASES

Disease identification is the first step in developing effective management programs for their control. Many states with established grape industries publish annual pest management guidelines and can be found online or at your local Cooperative Extension office. A non-exhaustive list includes:

New York and Pennsylvania grape pest management guidelines

Guidelines for Midwest states including Illinois, Indiana, Iowa, Kansas, Kentucky, Missouri, Nebraska, Ohio, Oklahoma, West Virginia, and Wisconsin can be found at:
https://ag.purdue.edu/hla/hort/pages/sfg_sprayguide.aspx

An excellent summary article of disease management spray programs for grapes, by Dr. Wayne Wilcox, Cornell University, can be found at:
https://doubleavineyards.com/kb/?s=wilcox&ht-kb-search=1

]]> Grape Phylloxera – Aerial or Foliar Form https://doubleavineyards.com/news/grape-phylloxera-aerial-or-foliar-form/ Fri, 28 Jun 2013 14:19:23 +0000 https://doubleavineyards.com/blog/?p=72  

Rick Dunst, Viticulturist, Double A Vineyards, Inc. 

 

It is the time of year when our office starts receiving calls about “bumps” forming on grape leaves. While pest identification is usually quite difficult when based solely on a rough description of the symptoms, “bumps” on grapevine leaves are almost always associated with the aerial, or leaf form, of phylloxera.

Phylloxera (Daktulosphaira vitifoliae) is probably the most well-known insect pest of grapevines across the world. Phylloxera was imported to Europe from the northeast United States in the mid-1850s, and the root form of this pest devastated European vinifera vineyards growing on their own roots. Most native American grape species are resistant or tolerant to root feeding, and eventually the European grape industry recovered by replanting vinifera on resistant rootstocks of North American origin.

In addition to the underground, root feeding form of phylloxera, there is also an aerial, or leaf-feeding form of the same insect species. Eggs deposited in the fall under the bark of a grapevine are the overwintering phase of the insect. The overwintering eggs hatch in early spring, and wingless female nymphs crawl to the shoot tips of newly emerging shoots. The nymphs insert their stylets into the upper surface of young expanding leaves, and a leaf gall develops around the insect, forming a hollow growth on the underside of the leaves inside which the insect continues to feed. After about two weeks, eggs are deposited inside the galls. As the eggs hatch, new nymphs emerge from the galls through a small exit hole on the upper surface of the leaf. The newly emerged nymphs crawl towards the shoot tip and begin feeding on expanding leaves, forming new galls. Five to seven generations of nymphs (and galls) can be produced in a growing season, with new injury always occurring on newly forming leaves.

There is wide variation in grape varietal susceptibility to leaf feeding and gall formation by phylloxera. In our experience, susceptible cultivars include Aurore’, Foch, Delaware, Marquette, Frontenac, and Frontenac Gris, while galls are rarely seen on Concord and most vinifera cultivars.

In many cases, the damage caused by leaf feeding and gall formation by phylloxera are considered “cosmetic” and not damaging to the vine, and many varieties can withstand extensive galling. However, in heavy infestations, galled leaves are malformed and rolled, causing a reduction in vine leaf area and potentially reducing photosynthesis. Severe infestations can cause defoliation and retard shoot growth. In such extreme cases, the loss of carbohydrates could result in reduced sugar levels at harvest, and a reduction in stored carbohydrates to support new vine growth the following spring.

There are few insecticide options for controlling the leaf form of phylloxera. Many common insecticides such as carbaryl (trade name Sevin) do not control this insect. In New York State, there are two non-restricted use insecticides registered for control of leaf phylloxera. Movento (spirotetramat is the active ingredient) is a relatively new (and expensive!) systemic insecticide that provides effective control of phylloxera. Movento is absorbed into leaves and is translocated throughout the plant, and can control nymphs feeding inside the leaf galls. Movento should be applied at the first signs of galling, and it can be applied a second time at least 30 days following the initial application. Assail (acetamiprid is the active ingredient) is a neonicitinoid insecticide that is very effective against sucking insects such as phylloxera. Assail should be applied when galls first start forming, and then reapplied 10-12 days later.

If you choose to use one of these insecticides in your vineyard, read the pesticide label, and consult University recommendations for your state.

REFERENCES

https://doubleavineyards.com/plant-diagnostic/problems/grape-phylloxera-foliar-form/
http://www.extension.org/pages/31606/grape-phylloxera-foliar-or-aerial

http://www.omafra.gov.on.ca/english/crops/facts/88-125.htm

https://ohiograpeweb.cfaes.ohio-state.edu/ipm/insects/grape-phylloxera

New York and Pennsylvania Pest Management Guidelines for Grapes

Guidelines for Midwest states including Illinois, Indiana, Iowa, Kansas, Kentucky, Missouri, Nebraska, Ohio, Oklahoma, West Virginia, and Wisconsin can be found at:
https://ag.purdue.edu/hla/hort/pages/sfg_sprayguide.aspx

]]> Pierce’s Disease of Grape https://doubleavineyards.com/news/pierces-disease-of-grape/ Thu, 21 Feb 2013 14:12:06 +0000 https://doubleavineyards.com/blog/?p=65 Rick Dunst, Viticulturist, Double A Vineyards, Inc.

With Jim Kamas, Assistant Professor & ExtensionSpecialist – Pomology & Viticulture, Texas A&M AgriLife Extension Service, Fredericksburg, Texas

Grape growers in southern regions of the United States face a potential problem not encountered by growers in more northern regions–Pierce’s disease (PD) of grape.  An excellent resource, Pierce’s Disease Overview and Management Guide – A Resource For Grape Growers in Texas and Other Eastern U.S. Growing Regions, has recently been published by a team of researchers at Texas AgriLife Extension Service and the University of Houston-Downtown.  This article will provide a brief summary of the information provided in this publication, as well as information about grape varietal susceptibility to this potentially devastating disease.

The link for the PD Overview and Management Guide can be found at:
http://aggie-horticulture.tamu.edu/fruit-nut/files/2010/10/Texas-Grape-Growers-PD-Management-Guide.pdf

Pierce’s disease was first reported near Anaheim, Californiain 1883, and by 1885 about half of the vineyard acreage near Anaheim was dead.  In the 1920s, Central Valley vineyards were affected, and by the 1930s, the first statewide epidemic was reported in California.  The disease has always been cyclic, but the introduction of Glassy-winged sharp shooter into southern California in the late 1990s dramatically changed the threat this disease poses in California.  Since then, numerous researchers have begun to unravel the origins and cause of the disease on both sides of the Rocky Mountains. Researchers now understand that PD moved from Texas to California on infected nursery stock, and it is now endemic in many parts of California.  Unfortunately, and for reasons not completely understood, the known range of Pierce’s Disease has moved further north than originally thought, into northern areas of the Gulf States, southern Missouri, Arizona and New Mexico and coastal areas of North Carolina and Virginia.  Possible reasons for the northern spread of PD include warmer climate, increased cold hardiness of the pathogen, and, as Jim likes to say “an increase in researchers looking for the disease.”

Pierce’s disease is caused by Xylella fastidiosa, a xylem-limited bacterium native to the Southeastern United States vectored by several insect pests, mainly xylemfeeding Cicadellid insect species.  Fortunately, the disease is intolerant to cold temperatures which limit the spread of the disease to more northern growing areas.

Symptoms of Pierce’s disease include leaf scorch, abscised leaf blades with retained petioles, uneven periderm formation, and shoot and cluster collapse (additional photos and information can be found at the links listed below). Once vines are infected, the disease can spread to additional vines, vectored by insects that contain the disease bacterium.   Vitis species vary greatly in their response to Pierce’s disease.  V.Labruscana, V. vinifera, and French-American varieties are susceptible to PD, but cultivars vary greatly in field longevity once infection has occurred. Other species and varieties are tolerant to the disease, meaning they have the ability to sustain infections by the pathogen with no reduction in yield.  Tolerant vines include ‘BlackSpanish’, ‘Blanc du Bois’, and most wild Vitis species native to the Gulf Coast and southeastern United States.  Finally, additional species and cultivars are resistant to PD, meaning they have the ability to limit colonization by the pathogen.  Resistant vines include Vitis arizonica, V. smallii, and some interesting new selections being developed in California by Dr. Andy Walker by crossing V.arizonica with traditional vinifera cultivars.

Management of Pierce’s disease is discussed at length in the Texas AgriLife publication.  In PD susceptible areas, sites should be chosen with limited or little to no perennial vegetation that harbors the insect vectors. Sites with perennial vegetation and access to water during the summer should be avoided.  Buffer areas of several hundred feet from perennial vegetation should be created, and susceptible hosts removed.  Insect vector control can be achieved using neonicotenoid insecticides, especially if applied through a drip irrigation system.   Vegetation in and around the vineyard should be mowed frequently to discourage attraction to insect vectors.  Infected vines should be removed from the vineyard as soon as disease symptoms become apparent to prevent disease spread to neighboring vines.

2_21_13-second-photoCurrent research in Texas focuses on the evaluation of resistant and tolerant grape varieties and rootstocks.  The University of Arkansas, Texas AgriLifeand Tarkington Vineyards have released ‘Victoria Red’, a new PD tolerant variety that holds strong promise for home and limited commercial production along the Gulf Coast.  Dr. Andy Walkerand others are using resistant native species with continued backcrossing with vinifera to produce new selections. Ongoing evaluation suggests some of these new selections are fully resistant to PD and exhibit high wine quality similar to their vinifera parents.  Another line of research involves intentionally infecting vines with non-virulent strains of Xyllella.  This appears to protect grapevines from infection by virulent strains of PD.

Grape cultivars often mentioned to be tolerant of Pierce’s disease include ‘Villard Blanc’, ‘Norton’, and ‘Chambourcin’.  The Texas AgriLife publication indicates ‘Villard Blanc’ is considered tolerant of PD.  ‘Norton’ appears somewhat tolerant, but underhigh pressure, ‘Norton’ can suffer from vine decline and eventual death.  I asked Jim to offer his view of the tolerance level of ‘Villard Blanc’, ‘Norton, and ‘Chambourcin’, and his reply follows:

“We consider most vinifera cultivars to be susceptible, but there is variation in how quickly vines exhibit symptoms.  ‘Chardonnay’ and ‘Sangiovese’ become symptomatic very soon after infection in warm climates but other varieties such as ‘Cabernet Sauvignon’ may take several years to show leaf scorch.  We have learned quite a lot about grapevine response to Xylella over the past ten years and the first point we need to think about is that inoculation does not necessarily mean infection.  One of the things that drives vine responseto this pathogen is the frequency and efficiency of being fed upon by vectors carrying the pathogen.  The response of ‘Norton’ is a prime example.  In the Gulf Coast of Texas where the disease pressure is severe, we expect that vines will be challenged by hot vectors many times a day. Under these conditions, ‘Norton’ will slowly start to exhibit symptoms, slowly start to decline, and lose vine size and productivity.  After a number of years, the vines are simply not productive and are usually removed by the grower.  We have pruned some of these declined vines to the ground and they produce vigorous new trunks that once again can return the vines to a moderate state of productivity, but they decline again pretty rapidly.  When ‘Norton’ vines are planted on low disease pressure vines in the Texas Hill Country, and cultural practices are followed to manage vectors and the disease, we expect that perhaps the vines are fed upon by competent vectors once or twice a week.  So far, under these conditions, ‘Norton’ has grown and been productive for at least ten years without a loss of vigor or productivity.”

“Similar experiences have been seen with ‘Chambourcin’, but in these cases it is typically vineyard management practices that affect vine longevity.When properly managed, and sustainable crop levels are produced,’Chambourcin’ will live for years with the disease.  But those who have grown ‘Chambourcin’ know all too well that it is prone to setting large crops.  When ‘Chambourcin’ is consistently overcropped, it declines and dies very rapidly. The same is generally true with ‘Villard Blanc’; it holds up to PD pretty well, but must be cared for and not overcropped.  ‘Villard Blanc’ has been used as a parent in breeding programs for powdery mildew resistance, but has apparently also provided some of the PD tolerance to varieties such as ‘Victoria Red’,’Phoenix’ and ‘Orion’.  All of these varieties with tolerance will show some symptoms, especially under heat and drought stress, but it’s their ability to maintain vine size and productivity that’s important.”

“In the northern parts of what we now consider the expanded PD zone, this pathogen is not always lethal.  Even though PD symptoms can be found in vineyards, cold temperatures appear to limit the degree of colonization of the vine.  Accordingly, we have come to view Xylella infection as a stress.  In areas that do not receive enough cold temperatures to affect the pathogen, this stress is acute and can (and does) kill grapevines.  In more northern areas, it is more of a chronic stress.  Combine Xylella infection with overcropping, drought stress, poor vineyard floor management, or any other factor that negatively affects vine health, and the effects of the disease are magnified.”

In summary, much has been learned about Pierce’s disease in the past decade.  The research conducted in Texas, especially, has provided insight into the spread of the disease tomore northern climates, has identified numerous insect vectors, and has developed integrated management techniques to limit the spread of the disease in vineyards.  Additionally, several researchers are evaluating new and old cultivars with increased resistance to the disease.  This article has provided only a brief summary of these efforts, and growers in Pierce’s disease susceptible regions are strongly urged to study the information provided in the links contained in this article.

Additional Links

Management of Pierce’s Disease in Texas

Growing Grapes in Texas, From the Commercial Vineyard to the Backyard Vine – Jim Kamas

]]> Sulfur Injury on Grapevines https://doubleavineyards.com/news/sulfur-injury-on-grapevines/ https://doubleavineyards.com/news/sulfur-injury-on-grapevines/#comments Fri, 19 Oct 2012 14:12:23 +0000 https://doubleavineyards.com/blog/?p=67  

Rick Dunst, Viticulturist, Double A Vineyards, Inc.

 

Powdery mildew (PM) is an important vineyard disease worldwide.  As pointed out by Cornell University grape plant pathologist Wayne Wilcox, Eastern North America is the origin of powdery mildew, and we cannot grow grapes here without controlling it.  Sulfur is a traditional material used to control powdery mildew, but grape cultivars differ widely in their susceptibility to injury from sulfur applications.

In warmer climates such as California, powdery mildew overwinters in infected buds that produce mildewed “flag shoots”.   In cooler climates, it overwinters as minute fruiting bodies called cleistothecia that lodge in the bark of vines.  In either case, fungal spores (ascospores) are released in the spring and infect new foliage and young clusters.  Subsequent spore release (from conidia) results in further disease development during the season, although grape varieties vary widely in their susceptibility to the disease.

Sulfur has been used to control powdery mildew around the world in many crops for about 150 years with no development of resistant strains of powdery mildew [1].  Sulfur is both inexpensive and effective in controlling powdery mildew, but it has limitations.  Sulfur provides very good protective activity on sprayed tissues (until it is washed off by rain), but not on new leaves that emerge after the last application. Wilcox’ research has shown that sulfur provides excellent post-infection control of PM until the time that young colonies start to become obvious, but post-infection sprays applied to heavily-diseased tissues are much less effective than those applied to incubating or very young colonies [2].  Some formulations of sulfur are considered “organic” (OMRI listed), and commercial grape growers often tank mix sulfur with synthetic powdery mildew fungicides as a disease resistance management strategy.

Grape cultivars differ widely in their susceptibility to sulfur injury.  Most vinifera varieties are sulfur tolerant (there are exceptions), and can be sprayed throughout the growing season without injury, but even sulfur-tolerant varieties can be injured if sprayed when temperatures are above 85°F.  Growers are advised to check with their buyers regarding cutoff dates for sulfur applications, as late season applications can result in off-odors and flavors in finished wine.  Many native and hybrid varieties are sulfur-sensitive, and some are susceptible to debilitating effects from sulfur injury.  For example, in a 2-year study (1991-1992) conducted at Cornell’s Vineyard Laboratory in Fredonia, NY, four annual applications of 4 lb. Microthiol 80DF reduced ‘Concord’ percent trellis fill, cane pruning weight, and yield by 31%, 34%, and 48%, respectively [3].

Double A Vineyards maintains about 40 acres of variety blocks for vine propagation.  In both 2011 and 2012, we intentionally sprayed our propagation blocks with two post-bloom applications of 6 lb. Microthiol DF at two week intervals, in order to update the information on sulfur sensitivity provided in our Grapevine Variety Characteristic Chart.  Each variety was rated on a scale of 0-2 for sulfur injury, based on a scale developed by Dr. Wayne Wilcox (Cornell), Dr. Lance Cadle-Davidson (USDA), and me in 2009 (photos accompany this article).  Our injury scale is: 0 = no apparent injury in either 2011 or 2012; 1 = minor visible injury observed in 2011 and/or 2012; and 2 = substantial visible injury observed in 2011 and/or 2012. On some varieties, injury was more severe in 2012 under warmer and drier conditions, and the higher rating is indicated in our chart.  In practical terms, a “2” rating on our sulfur injury scale indicates substantial risk to vine health and productivity from sulfur injury, and sulfur application is strongly advised against.  A “1” rating indicates some minor injury may be observed, and caution is advised, especially when air temperatures are 85°F or above at the time of application.  In cases where Double A Vineyards does not grow our own propagation wood on premises, we rely on information provided by various University sources, especially Cornell, Ohio State, Virginia Tech, and local growers.

The sulfur sensitivity information in our updated Grapevine Variety Characteristic Chart is meant as a guideline that represents our experience, and that of others, to assist you in determining the advisability of including sulfur in your disease management program, but does not guarantee that greater injury may occur from sulfur applications made under different conditions.  We hope you find this information useful!

[1]  Strategies to Control Powdery Mildew, Wayne Wilcox, 2003.

[2] 2017 & 2018 Grape Disease Control – Wayne F. Wilcox

[3]  Whole Farm Impact of Converting Conventionally Managed Eastern Vineyards to Organic Management Practices, Roger Pearson (project coordinator), 1992.  SARE Project 92-10-01.

]]> https://doubleavineyards.com/news/sulfur-injury-on-grapevines/feed/ 1 Dealing with Yellow Jackets in the Vineyard https://doubleavineyards.com/news/dealing-with-yellow-jackets-in-the-vineyard/ Wed, 29 Aug 2012 14:19:48 +0000 https://doubleavineyards.com/blog/?p=74  

Rick Dunst, Viticulturist, Double A Vineyards, Inc.

 

This month’s article is inspired by several e-mails and phone calls received over the past few weeks from all over the country regarding yellow jackets in vineyards and how to control them.  Unfortunately, there are no easy solutions to this group of insects, and they can pose a stinging hazard, especially to workers harvesting ripe fruit in the vineyard.

IDENTIFICATION

There are several species of yellow jackets (Vespula species) that can be found across the United States.  Yellow jackets are considered a “beneficial” insect because they pollinate plants and they are predators that feed on insect pests of grapes and other crops.  However, yellow jackets also feed on sources of sugar, such as ripe grapes and other fruit crops.

Despite their “anti-social” reputation, many bee and wasp species are social insects with organized colonies.  Social wasps include yellow jackets, hornets, and paper wasps, and they all build paper combs called “cartons”.  Depending on the species, nests can be built in natural cavities in trees, underneath awnings, in crevices such as in metal vineyard posts, and also in underground rodent burrows.  Populations increase during the summer so that by late summer, a colony may contain several hundreds or thousands of individuals that will aggressively defend their nests from intruders.   Photos of yellow jackets, bees, and wasp species can be found in references listed at the end of this article.

LIFE CYCLE

Yellow jacket colonies are started in the spring by a single mated queen that has survived the winter.  Queens begin the colony by gathering wood pulp used to create the first cells for the nest.  Eggs are laid and the queen provides for the first brood of workers.  Once the workers emerge as adults, they take over the tasks of nest expansion, brood care, and foraging, while the queen spends the rest of her life laying eggs.  Colonies grow through the summer and, as mentioned, can reach hundreds or thousands of individuals.  Early in the season yellow jackets prey mainly on other insects to provide protein for developing larvae.  Once the colony is well established, yellow jackets turn to sugar as the primary food source, and ripening grapes can be an attractive source of food.

MANAGING YELLOW JACKETS IN THE VINEYARD

Managing yellow jackets in the vineyard can be a difficult task  To some extent, once the problem exists it can be very difficult to deal with.  Prevention can be the best solution.

Although yellow jackets can feed directly on sound fruit, they are usually attracted initially to damaged grape berries.  A key to yellow jacket management is keeping the fruit intact by controlling bird predation and by preventing fruit splitting from cluster diseases (to the extent possible).  Alice Wise, viticulture researcher and grape guru at the Long Island Horticultural Research and Extension Lab in Riverhead, NY, reports excellent results controlling birds AND yellow jackets using exclusionary, fine mesh nets.  This recommendation comes from someone growing grapes under difficult grape growing conditions on a migratory bird pathway.

Limiting the availability of attractive food sources in and around the vineyard can help reduce yellow jacket populations.  Fallen fruit from vines and other fruit crops should be removed from the vineyard when possible.
Trapping individual yellow jackets can reduce their population to some extent.  Traps containing food-based attractants are commercially available, and there are several homemade trap designs that can be found on the internet.  Google “homemade yellow jacket traps.”

Yellow jackets feed during the day and their nests can often be found by following individuals back to the nest.  Before attempting to destroy a nest, carefully consider the consequences and circumstances.  Recall that honeybees have a detachable stinger, so can only sting once.  Yellow jackets have a retractable stinger that can be used several times, and dead or injured insects can release pheromones that attract other insects from the same nest.  Protective gear should be worn, and individuals allergic to bee stings should not conduct this work.  Professional exterminators are available in many locations.

Broadcast insecticide applications are not recommended to control yellow jackets as they are ineffective, and most insecticides cannot be used for this purpose.  There are, however, many commercially available insecticide products that can be used when directed at individual insects or at the entrance to a nest.  Applications to the nest should be performed at night, when the insects are in the nest, and are best done when air temperatures are cooler and the yellow jackets are less active.

Finally, if yellow jackets pose an annual problem in your vineyard, consider trapping them in spring and early summer when colony populations are lower.  Trapping in early spring can eliminate the queens responsible for establishing new colonies.  Food-based traps can be effective in eliminating small numbers of insects, but the attractant needs to be kept fresh by replacing on a regular basis.

REFERENCES
https://conservancy.umn.edu/bitstream/handle/11299/166875/Grape%20IPM%20Guide.pdf?sequence=1&isAllowed=y
https://www.gardeners.com/how-to/yellow-jackets/7700.html
http://www.ehow.com/how_8670468_kill-yellow-jacket-bee.html
Wasp and Bee Management, Jody Gangloff-Kaufmann, NYSIPM Program, available at www.nraes.org

]]> Minimizing Bird Damage in your Vineyards https://doubleavineyards.com/news/minimizing-bird-damage-in-your-vineyards/ Tue, 14 Aug 2012 14:20:20 +0000 https://doubleavineyards.com/blog/?p=76

Rick Dunst, Viticulturist, Double A Vineyards, Inc.

 

After successfully managing a crop to within weeks or even days of harvest, few things can be as frustrating as fruit damaged by birds and other pests.  In addition to direct loss of fruit, bird-damaged fruit is also more susceptible to various fruit rots that can cause off-flavors and other defects in wine.  This article will summarize a few practices that can reduce bird-damaged fruit in vineyards.

SOUND DEVICE

There are two main types of sound devices used to deter bird feeding: “gunshot” sound can be used to give unexpected sound blasts that cause birds to scatter.  They can also serve as a source of strife between grape growers and their neighbors, so they are generally used only in more rural settings. Bird scare devices, such as BirdGard®, produce electronic sounds that mimic bird distress calls and/or calls of predatory birds and are generally considered less annoying to neighbors than sound blasts.  The keys to successful use of electronic sound devices include placing the devices before, or at the initiation of, bird feeding; changing the pattern, frequency, and specific calls being used every few days; and changing the position of the device in the vineyard.  Birds tend to habituate to noises over time, so making the noises less predictable can increase their effectiveness.

VISUAL DETERRENTS

Visual deterrents take the form of reflective tape, aluminum pie plates, and artificial predatory animals.  In our experience, reflective tape has been an effective technique, especially when growers saturate an area by tying the tape overhead, on gaps in the trellis, and to a perimeter wire.

PHYSICAL BARRIER

When all else fails, bird netting is often the best solution, but it may require a fair amount of labor to install.  Depending on pressure, birds can feed through the netting, or find gaps at seams or under the trellis.  Typical bird netting is applied either by hand (three people are needed) or with tractor-mounted applicators.  Side netting for vertical shoot positioned (VSP) trained vineyards is available, as is overhead netting that is draped over the trellis and fastened underneath.

Double A Vineyards sells AviGard® overhead bird netting that has proven to be effective in our experience.  AviGard® netting is ¾” mesh made from high density polyethylene rip-stop yarn.

USING AN INTEGRATED APPROACH TO BIRD CONTROL

One method of bird deterrent may only be effective for a short period of time.  Use a combination of methods such as visual deterrents and sound devices.  Create unexpected noises by changing distress calls every few days, and by repositioning them at different positions in and around the vineyard.  Under conditions of high bird predation, netting may be necessary to save the crop.

For more information about reducing bird and other wildlife damage in grapes, refer to Chapter 7 in the Midwest Small Fruit Pest Management Handbook. https://extensionpubs.osu.edu/midwest-small-fruit-pest-management-handbook-pdf/

]]>