Strategies for Managing Phytophthora Blight Chris Smart, Holly Lange, Amara Dunn, Lisa Jones and Maryn Carlson Cornell University Geneva, NY
Growing squash has become difficult!
Phytophthora Blight Phytophthora capsici
Wide Host Range
Wilting and plant death Crown and root rot Fruit rot Stem and leaf lesions Symptoms
Symptoms on Squash
Phytophthora Blight Phytophthora capsici Infected plants and fruit produce millions of spores One spore will produce 20-40 zoospores swimmers Pathogen spreads in water splashing rain, irrigation These asexual spores are called sporangia Oospores can survive for years in soil, and will infect roots or fruit when conditions are favorable A1 A2 If both mating types are present, oospores produced Infected plant dies, pathogen remains in debris
What do spores look like? Sporangia Zoospores Oospores
Potential for rapid spread in a field 1 spaghetti squash 44 million sporangia 880 million zoospores
Pcap in NY what have we learned? 28 fields sampled 257 isolates WNY CNY CD LI Original samples 2006-2009 Many more fields sampled since 2009
What do we know? Both mating types are present in NY s vegetable fields Regional differences in mefenoxam sensitivity No resistant isolates found in WNY or CNY (2009), but we identified a field with resistant isolates in WNY in 2011 In CD, 66% of isolates were resistant In LI, 25% of isolates were either partially or fully resistant
How Does Phytophthora Move? Culled fruit Cultivation Soil (tractor tires) Rain water/splashing Irrigation water Flood water Does not move in air/wind
Cull Piles
Surface Irrigation Water 60% of NY vegetables are irrigated with surface irrigation water
Irrigation Sources Creeks Irrigation Ponds Erie Canal
Surface Irrigation Water 60% of NY vegetables are irrigated with surface irrigation water Surveyed 20 sites across NY for Phytophthora capsici once a month for 2 years pathogen can be present in water Improving detection methods to identify pathogens quickly Comparing methods for decontamination
Pictures on left from the NY Times Irene and Lee
P. capsici from flooded fields Collected from five fields with no history of Phytophthora blight Have data on isolates from three of the five fields Some diversity (not all isolates are the same) Most mefenoxam resistant Working with growers, developing management plans
What are we working on now? Making great use of the blight farm Testing potential resistant varieties with a diversity of isolates from NY Working with public and private breeders Several projects with Michael Mazourek Testing isolates for fungicide resistance Continue to study diversity, and changes that may occur over time in the field How do resistant varieties stop the pathogen
Management Strategies If you don t have Phytophthora blight KEEP IT OFF YOUR FARM! If you have Phytophthora blight Promote good drainage Choose tolerant varieties Rotate Rogue if possible Use effective fungicides (ROTATE CHEMISTRIES)
Management Strategies Commonly used fungicides Ranman Presidio (18-month plant-back restriction) Gavel Forum Revus Tanos Phosphorous acid fungicides Ridomil (perhaps once/season in Western NY)
Cucurbit Downy Mildew Pseudoperonospora cubensis Attacks all cucurbits cucumbers most susceptible
Cucurbit Downy Mildew Caused by Pseudoperonospora cubensis A water mold related to Phytophthora Attacks all cucurbits cucumbers most susceptible, but melon, pumpkin and other cucurbits also susceptible Present every year
First symptom is a yellowing spot on the upper surface of the leaf Spots expand turning tan and papery, but are bordered by veins Lower leaf surface has gray spores Symptoms
Young Lesion
Older Lesion
Bottom of Leaf
Downy and Powdery on Winter Squash
Mildews Powdery Mildew Downy Mildew
Downy Control The pathogen blows in either from the south, or from greenhouse production, and generally does not arrive until late July No commercially available squash resistant to the strains we have but squash and pumpkin are less susceptible than cucumber or melon Vegetable news letters provide information on where downy has been reported Excellent website http://cdm.ipmpipe.org/ Sign up for alerts
Downy Control The downy mildew pathogen is closely related to Phytophthora (both are water molds), many fungicides that are effective against downy are also labeled for Phytophthora blight Broad-spectrum protectant fungicides provide some control Follow outbreaks and know when the pathogen is in the area
Thanks! Smart lab members Grower cooperators Vegetable Extension Educators NYS Ag Expt Station NYS Dept of Ag and Mkts USDA - NIFA
Questions?