POWDERY MILDEW MANAGEMENT: THE GOLDILOCKS PRINCIPLE

Transcription

1 World Class. Face to Face. Sustainable Ag Expo San Luis Obispo November 2015 POWDERY MILDEW MANAGEMENT: THE GOLDILOCKS PRINCIPLE Michelle M. Moyer, Ph.D. Assistant Professor Statewide Viticulture Extension Specialist WSU-IAREC Prosser, WA wine.wsu.edu

2 THE GOLDILOCKS PRINCIPLE / PARADOX must fall within certain margins, as opposed to reaching extremes Goldilocks likes things just right The powdery mildew fungus likes things just right

3 THE PORRIDGE IS TOO Temperature effects on Powdery Mildew Image from:

4 Choudhury, R Thesis. Consecutive Heat Acclimation and Modeling Uncertainty for Grapevine Powdery Mildew. UC-Davis, USA PM DOESN T LIKE IT TOO HOT Single heat events (89-95ºF) can debilitate or kill the PM fungus Consecutive heating events do not add to damage Multiple, high-heat (99-102ºF) events can have accumulating effects on colony growth Heat events must be sustained at 1 hr Heat exposure events can delay sporulation

5 Moyer, M.M., et. al Phytopathology 100: PM DOESN T LIKE IT TOO COLD Four-day-old colony grown at 75ºF: A) A fungal colony, and B) Same colony with a live stain (green = alive) Four-day-old colony exposed to 36ºF for 8 h at 3 days old: C) A fungal colony, and D) Same colony with a live stain

6 Delp, C.J Phytopathology 44: PM LIKES THE TEMP JUST RIGHT 100 % Germination ºF 77ºF 95ºF Temperature ( C)

7 PM DOESN T LIKE IT TOO SUNNY Photos courtesy Dr. Craig N. Austin, DuPont

8 PM DOESN T LIKE IT TOO DRY Carroll, J. et. al Phytopathology. 93:

9 THAT CHAIR IS TOO BIG! Plant Susceptibility to Infection Image from:

10 ONTOGENIC SUSCEPTIBILITY Grape berries, and leaves display increasing levels of resistance Berries completely resistant within 1 month post-bloom Infection can start early (cluster emergence), but likelihood is a function of target size

11 Image from: Merry, et. al.2013, Plant Pathology 62: ONTOGENIC RESISTANCE LEAVES Arrow indicates the leaf that is no longer importing assimilates Challenges with identifying this: Works only when shoots are actively growing Lateral shoots can have susceptible and resistant leaves If shoot growth is stopped, leaf positioning no longer maintains importance

12 Image from: Merry, et. al.2013, Plant Pathology 62: ONTOGENIC RESISTANCE LEAVES Transitioning leaves are simultaneously sources and sinks maximum assimilate in tissue Newly developing leaves are not the most susceptible Related to actual infection frequency Related to target size

13 Ficke, et. al Phytopathology 93: ONTOGENIC RESISTANCE GRAPE BERRIES Chardonnay Concord Chardonnay

14 WHEN EVERYTHING IS JUST RIGHT Goldilocks stops complaining. Finally. Powdery mildew makes a break for it. Unfortunately.

15 Sometimes, when everything is just right, you need to make it all wrong.

16 HOW TO MAKE THINGS NOT RIGHT FOR PM Disease on fruit is related to two key factors: 1. Disease pressure via the environment 2. Ontogenic susceptibility / likelihood of infection To avoid disease, avoid/manipulate/change these. To prevent Goldilocks from breaking and entering, stop displaying the goods and/or get a security system.

17 MAKE THE TIMING NOT RIGHT Cleistothecia prefer moderate temperature Older leaves (larger) support more cleistothecia but they were infected young! 1 June = 152; 1 Aug = 213; 1 Sept = 244 Gadoury, et. al Phytopathology 78:

18 Moyer, et. al AJEV 65: ENVIRONMENTAL PRESSURE Low-Pressure Year High-Pressure Year In low diseasepressure years, poor spray programs can still work, regardless of primary inoculum In high-pressure years, a spray program AND control of primary inoculum is important

19 Cartoon from: HOW TO AVOID THE JUST RIGHT Adjust the canopy to improve sunlight, air circulation, and surface temperature Prebloom fruit-zone leaf removal BEFORE Prebloom fruit-zone leaf removal AFTER

20 HOW TO AVOID THE JUST RIGHT There are two ways to avoid severe disease outbreaks: 1. Misalign fungal development and plant development 2. Protect susceptible fruit during the just right window

21 CRITICAL WINDOWS CONTROL OF FRUIT DISEASE Ontogenic resistance can help fruit escape infection, if disease progress is delayed Delay through reducing disease progress rates

22 PRIMARY INOCULUM TIMING Moyer, et. al AJEV 65:

23 EXAMPLES FUNGICIDES EARLY SEASON Contact fungicides Work great if an infection period was missed Do not provide coverage for active growth Systemic fungicides Will move to protect new growth BUT if not a lot of tissue is available during application you aren t getting as much absorbed Translaminar fungicides Can help with coverage, but coverage is generally not an early-season issue

24 THE CRITICAL WINDOW What to do: Use your best available products Rotate FRAC codes Use dual-action products during bloom to pea-size berries (PM and BBR control) Use higher rates, shorter intervals CANOPY MANAGEMENT What to avoid: Repeated use of the same product EXTENDED SPRAY INTERVALS Low water volumes if canopies are larger PRODUCTS WITH SUPPRESSION ACTIVITY

25 DETERMINING GOLDILOCKS S TRIPS When will things be a problem?

26 UC-DAVIS PM INDEX Model has 1 infection table (leaf wetness) Main-season model ( conidial ) driven on high temperatures Poor PM development at high temps Aimed to reduce total sprays

27 Meeting Abstracts/aps2013abO07.htm AERIAL PM MONITORING USDA / OREGON STATE Air detection of spores Useful in earlyseason spray program development Useful with products that have slight eradicant activity

28 THE NEW CALENDAR SPRAY SCHEDULE Adopted from : Moyer, M.M. et. al Plant Disease,

29 AND THEY LIVED HAPPILY EVER AFTER. Sometimes Goldilocks learns her lesson. Sometimes she gets eaten by the bears. Either way, the bears win.

30 WINNING IS ABOUT TIMING Be these Bears Not this Bear Family of Bears Stops a Would-Be Burglar With Impeccably-Timed Return He s no Aaron Rodgers.

31 QUESTIONS? VITICULTURE EXTENSION WASHINGTON STATE UNIVERSITY World Class. Face to Face. Office: