Cucurbit Downy Mildew Found in Haywood County–July 18, 2022

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Cucumber downy mildew (CDM) has been confirmed on cucumber plant samples from a homeowner garden in Haywood County, NC. Leaves showed symptoms typical of CDM: angular, chlorotic or yellow lesions on the upper surface of the leaves with gray to black spores on the underside of the leaf.

Update (7-19-22): Cucumber downy mildew was also reported in Avery County, NC in a community garden.

A broad green leaf with patches of yellow.

Symptoms of cucumber downy mildew (I. Meadows)

Growers in western NC are advised to implement management strategies. Effective fungicides can be found in the Southeastern US Vegetable Crop Handbook. More information can be found on the cucurbit downy mildew disease fact sheet.

This pathogen can rapidly become resistant to fungicides so, it is important to rotate fungicide groups and use tank mixes with protectants to minimize the risk of fungicide resistance. Cucumbers and cantaloupes are generally more susceptible to the disease than squash, watermelon, and pumpkin.

A mass of green natural material with specks of black in it.

Pseudoperonospora cubensis clade 2 sporangia under a dissecting microscope (Mariana Prieto, NC State Vegetable Pathology Lab)

Because this pathogen travels through air currents, it can spread rapidly. Therefore, it is important that growers report outbreaks so other growers in the area can implement management strategies.

You can track the spread of CDM and report outbreaks anonymously on the Cucurbit Downy Mildew IPM PIPE (CDM ipmPIPE). If you see symptoms of CDM in your cucurbits, please notify your local Extension Agent to assist in diagnosis and to help you send a sample to the Plant Disease and Insect Clinic.

Written By

Inga Meadows, N.C. Cooperative ExtensionInga MeadowsExtension Associate, Vegetable and Herbaceous Ornamental Pathology Call Inga Email Inga Entomology & Plant Pathology
NC State Extension, NC State University
Updated on Jul 19, 2022
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