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Chris Smart Plant Pathology and Plant- Microbe Biology Cornell University Geneva, NY Review of 2013 Vine Crop Diseases

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Chris Smart Plant Pathology and Plant-

Microbe Biology Cornell University

Geneva, NY

Review of 2013 Vine Crop Diseases

Growing vine crops has become difficult!

Common Diseases

• Powdery mildew • Virus diseases • Downy mildew • Phytophthora blight

Powdery Mildew Podosphaera xanthii

• VERY common – we see it every year

• Some varieties have resistance

• Kills leaves – Sun scald

• Weakens handles in pumpkins

• More susceptible to some other diseases

Powdery Mildew

• Evidence that the pathogen can overcome some plant resistance – This is still the way to go!

• That the pathogen can overcome some fungicides

• Effective fungicides (conventional and organic) are available

Common Diseases

• Powdery mildew • Virus diseases • Downy mildew • Phytophthora blight

Virus Diseases

• Watermelon Mosaic – present every year, arrives later in the season

• Cucumber Mosaic –not here every year or in every field, arrives early

• Aphid transmitted • Post bloom – only foliar

symptoms • Pre-bloom – fruit

symptoms Photo: Marc Fuchs

Virus symptoms

Cucumber Mosaic Watermelon Mosaic Photo: Marc Fuchs

Common Diseases

• Powdery mildew • Virus diseases • Downy mildew • Phytophthora blight

Cucurbit Downy Mildew Pseudoperonospora cubensis

Attacks all cucurbits – cucumbers most susceptible

Symptoms • 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

Lesions

Bottom of Leaf

Mildews

Powdery Mildew

Downy Mildew

Downy Control • The pathogen blows in either from the south,

or from greenhouse production around lakes Erie and Ontario, and generally does not arrive until late July or August – In Eastern NY, inoculum could come from either

source, and usually arrives later in the season • No commercially available resistant cucurbits

– but I am working with several breeders and we have high hopes!

• 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 – Many water-mold specific fungicides – Broad-spectrum protectant fungicides provide

some control • Follow outbreaks and know when the

pathogen is in the area

Common Diseases

• Powdery mildew • Virus diseases • Downy mildew • Phytophthora blight

Phytophthora Blight Phytophthora capsici

Wide Host Range

Symptoms • Wilting and plant

death – Crown and root rot

• Fruit rot • Stem and leaf

lesions

Phytophthora Blight

• Over winters as thick-walled spores in the soil

• Small white spores produced during the growing season, can’t survive over winter

• Swimming spores also produced

What do spores look like?

Oospores Sporangia Zoospores

How Does Phytophthora Move?

• Culled fruit • Cultivation • Soil (tractor tires) • Rain

water/splashing • Irrigation water • Flood water • Does not move in

air/wind

Surface Irrigation Water • 60% of NY vegetables are irrigated with

surface irrigation water

Irrigation Sources

Irrigation Ponds

Creeks

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

What are we working on now?

• Making great use of the ‘blight farm’

Blight Farm

• Five faculty now have P. capsici projects • Testing different varieties for resistance • Testing integrated control strategies • Ways to improve soil health – cover crops • Pathogen detection • Four 2-acre blocks, one block is organic

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)

Thanks! • Smart lab members • Grower cooperators • Vegetable Extension

Educators • NYS Ag Expt Station • NYS Dept of Ag and

Mkts • USDA - NIFA

Questions?