Powdery Mildew Control on Grapes in the San Joaquin Valley

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1 Powdery Mildew Control on Grapes in the San Joaquin Valley Allison Ferry-Abee Vi/culture Farm Advisor Tulare and Kings Coun/es

2 Impacts of Powdery Mildew All grapes Can reduce photosynthesis, reducing brix Early infec/ons cause berry scarring and stunted berries Predisposes berries to bunch rot and post harvest infec/ons Table grapes aesthe/c infec/ons on the berries and rachis

3 Powdery Mildew Disease Cycle: Erysiphe necator

4 of Grape to Powdery Mildew Risk Wine Table Raisin High Chardonnay Autumn King Fiesta Chenin blanc Crimson Seedless Zante Currant Muscat blanc Flame Seedless DOVine Red Globe Moderate Barbera Autumn Royal Thompson seedless Cabernet Sauvignon Selma Pete Pinot noir Syrah Zinfandel Low French Columbard Merlot Sangiovese

5 Control Cultural Canopy management Leaf pulling Hedging Sterile shoot removal Benefits Reduces humidity in the canopy Increases UV light that reaches the canopy Increased spray coverage

6 Fungicide

7 Control Sulfur Virtually no risk of developing resistance When canopies are very small at the beginning of the season (less than 12 growth) use a micronized sprayable formula/on of sulfur to prevent drix For larger canopies, sulfur is more effec/ve as a dust. It is worth it to buy a sulfur duster if you have more than a couple of acres of grapes! Do not apply when temperatures exceed 100⁰ F, or will soon axer applica/on Conven/onal: Use in the beginning of the season before switching to DMI and strobilurin fungicides Organic: Use in the beginning of the season before switching to biologicals

8 Control Oil (1-2%) Virtually no risk of developing resistance One of the only eradicants for powdery mildew most fungicides only prevent infec/on Use JMS Stylet oil (or other highly refined oils) to prevent phytotoxicity NEVER apply oil and sulfur within 2 weeks of each other Don t apply to table grapes axer berry set

9 Control for Low Disease Pressure SoX chemistries Potassium bicarbonate (make sure to use it with a spreader-s/cker) Biological controls Serenade (Bacillus sub*lis) Sonata (Bacillus pumilis)

10 Control for Moderate to High Disease Pressure Demethyla/on Inhibitors (FRAC Group 3, moderate resistance risk) Elite Vi/cure Rally Vintage Strobilurins (FRAC Group 11, high resistance risk) Abound Flint Sovran Quinolines (FRAC Group 13) Quintec Benzophenone (FRAC Group Unknown U8) Vivando Phenyl-Acetamide (FRAC Group Unknown U6) Torino Do not apply more than 2 consecu/ve applica/ons of fungicides from each FRAC Group

11 Timing

12 Gubler-Thomas Powdery Mildew Risk Index Based on the op/mal condi/ons for powdery mildew sporula/on and infec/on. Pay ahen/on to the risk index for the en/re powdery mildew treatment season. For prac/cal purposes, in the central and southern San Joaquin Valley, this means from 50% budbreak to 12⁰ brix, or un/l harvest for table grapes.

13 Powdery Mildew Risk Index Spray Material Spray Interval 0 to 30 sulfur dust 14 days or max label micronized sulfur 18 days or max label DMI fungicides 21 days or max label Strobilurins 21 days or max label Biologicals 7 to 14 days 40 to 50 sulfur dust 10 days micronized sulfur 14 days DMI fungicides 17 days Strobilurins 21 days Biologicals 7 days 60 to 100 sulfur dust 7 days micronized sulfur 10 days DMI fungicides 14 days or min label Strobilurins 14 days or min label Biologicals Use not recommended

14 Gubler-Thomas Powdery Mildew Risk Assessment Index Risk assessment index begins : EITHER at Ascospore release: When a certain number of hours of leaf wetness occur at various temperatures OR at Conidia germina/on: When there are three consecu/ve days with six consecu/ve hours between 70 and 85 degrees

15 Gubler-Thomas Powdery Mildew Risk Assessment Index Risk assessment index begins : EITHER at Ascospore release: When a certain number of hours of leaf wetness occur at various temperatures OR at Conidia germina/on: When there are three consecu/ve days with six consecu/ve hours between 70 and 85 degrees

16 An epidemic will begin when there are 3 consecutive days with 6 or more continuous hours of temperatures between 70 and 85 F as measured in the vine canopy. 1. Starting with the index at 0 on the first day, add 20 points for each day with 6 or more continuous hours of temperatures between 70 and 85 F. 2. If the index reaches 60, an epidemic is under way. 3.Each day, starting on the day after the index reached 60 points during the start phase, evaluate the temperatures and adjust the previous day's index according to the rules below. Keep a running tabulation throughout the season. In assigning points, note the following: If the index is already at 100, you can't add points. If the index is already at 0, you can't subtract points. If fewer than 6 continuous hours of temperatures between 70 and 85 F occurred, subtract 10 points. If 6 or more continuous hours of temperatures between 70 and 85 F occurred, add 20 points. If temperatures reached 95 F for more than 15 minutes, subtract 10 points. If there are 6 or more continuous hours with temperatures between 70 and 85 F AND the temperature rises to or above 95 F for at least 15 minutes, add 10 points.

17 hhp://ipm.ucanr.edu/calludt.cgi/grapepmview1

18 The most fungicide? Coverage, coverage, coverage! and calibra/on!

19 Applying Powdery Mildew Fungicides -Flat fan nozzles tend to be more effec/ve than cone nozzles -Try to op/mize pressure between crea/ng leaf movement and not folding leaves in half

20 Water sensi/ve and oil sensi/ve spray paper available from Gempler s ($60/50) Close to runoff Not enough coverage

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22 Powdery Mildew Control Updates Field trials conducted by Doug Gubler, CE Specialist at UC Davis and Trang Nguyen Rela/vely high disease pressure Conducted at Herzog Ranch, Courtland CA on Chardonnay Treatments began pre-bloom (April 14 in test plots) Treatments applied with handgun sprayers

23 Treatment Spray Interval Incidence Severity Untreated Control n/a 100% a 100% a Rally (5 oz/a) plus Regalia (2 quarts/a) 14 days 82% a 100% a JMS Stylet oil (0.5% v/v) alternated with Regalia (2qt/A) 7 days 67% ab 100% a Rally (5 oz/a) 14 days 67% ab 100% a JMS Stylet oil (0.5% v/v) alternated with Regalia (4qt/A) then JMS Stylet oil (0.5% v/v) then Luna Experience (6 fl oz) 7 days, 21 days axer Luna 56% b 94% ab Rally (5 oz/a) alternated with Regalia (2 quarts/a) 14 days axer Rally, 7 days axer Regalia 54% bc 98% a Regalia (2 quarts/a) alternated with Luna Experience (6 fl oz/a) then Pris/ne (8 oz/a) then Flint (2 oz/a) JMS Stylet oil (0.5% v/v) then Luna Experience (6 fl oz/a) then Regalia (2 quarts/a) then Flint (2 oz/ A) Regalia 2x, 7 days; Luna Experience, 21 days; Pris/ne, 14 days; Flint, 14 days 34% cd 91% b JMS Stylet, 7 days; Luna Experience, 21 days; Regalia, 7 days; Flint, 14 days 24% d 85% ab

24 Treatment Adjuvant Treatment Interval Severity Incidence Untreated control n/a n/a 98% a 100% a Pris/ne (14.5 oz/a) 0.25% v/v Dyneamic 21 days 35% b 99% a Mehle (5 oz/a) alternated with Pris/ne (10.5 oz/a) then Mehle (5 oz/a) then Tornio SC (3.4 fl oz/a) then Quintec (6 fl oz/a) then Torino SC (3.4 fl oz/a) 0.125% v/v Dyneamic days, based on Risk Index 33% b 100% a Rhyme (2.5 fl oz/a) none 14 days 32% b 100% a Vi/cure (6 fl oz/a) alternated with Pris/ne (8 oz/a) none 14 days 30% bc 98% a Sovran (4 oz/a) alternated with Rhyme (5 fl oz/a) then Quintec (4 fl oz/a) none 14 days 21% bcd 98% a Vi/cure (6 fl oz/a) alternated with Quintec (4 oz/a) none 14 days 16% cde 96% a days, based on Risk Index 15% def 91% ab Torino SC (3.4 fl oz) 0.125% v/v Dyneamic Rally (5 oz/a) alternated with Quintec (4 fl oz) 0.25% v/v Dyneamic 14 days 14% defg 90% ab Rhyme (5 fl oz/a) none 14 days 13% defg 97% a Inspire Super (20 fl oz/a) alternated with Quintec (4 fl oz/a) then Inspire Super (20 fl oz/ A) then Taegro (5.2 fl oz/a) 0.125% v/v Dyneamic 14 days 13% defg 86% abc Torino SC (3.4 fl oz) then Quintec (4 fl oz/a) 0.25% v/v Dyneamic 14 days 6% efg 70% c Mehle (5 oz/a) alternated with Pris/ne (10.5 oz/a) then Torino SC (3.4 fl oz/a) then Mehle (5 oz/a) then Tornio SC (3.4 fl oz/a) then Quintec (6 fl oz/a) 0.125% v/v Dyneamic days, based on Risk Index 6% efg 76% bc days, based on Risk Index 5.6% efg 69% c Mehle (5 oz/a) 0.125% v/v Dyneamic Quintec (6.6 fl oz/a) 0.25% v/v Dyneamic 21 days 5.6% efg 85% abc Inspire Super (20 fl oz/a) alternated with Quintec (4 fl oz/a) 0.125% v/v Dyneamic 14 days 2% efg 38% d Pris/ne (10.5 oz/a) alternated with Quintec (6.6 fl oz/a) 0.25% v/v Dyneamic 21 days 1.4% efg 36% d Luna Experience (8 fl oz/a)) Syl-Coat (4 fl oz/100 gal) 21 days (from bloom) 1.2% fg 39% g Luna Tranquility (16 fl oz/a) Syl-Coat (4 fl oz/100 gal) 21 days (from bloom) 0.16% g 4.8% e Luna Experience (6 fl oz/a) alternated with Quintec (4 fl oz/a) then Luna Tranquility (16 fl oz/a) then Sonata ASO (3 quarts/a) then Flint (2 oz/a) then Turino SC (3.4 fl oz/a) Syl-Coat (4 fl oz/100 gal) 14 days (from bloom) 0.09% g 5.6% e Luna Experience (8 fl oz) alternated with Quintec (6.6 fl oz) 0.25% v/v Dyneamic 21 days 0.09% g 4.8% e

25 Powdery Mildew Trial Results Doug Gubler s Powdery Mildew Fungicide Trial Results hhp://plantpathology.ucdavis.edu/coopera/ve_extension/

26 Thanks! (559)