Watermelon Downy Mildew Reported in North Carolina

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Downy mildew, caused by the oomycete Pseudoperonospora cubensis, has been reported in watermelon in North Carolina. It was observed in Nash county (June 17, 2016) and the field presented 5% incidence with each infected plant/leaf having 50% severity. A recent report from Johnston county (June 23, 2016) was from a watermelon field with 5% incidence and 30% severity. A previous report earlier this month (June 1st, 2016) was on cucumber in Duplin county.

Cucurbit downy mildew affects the leaves of all commercial cucurbits (cucumber, cantaloupe, squash, watermelon, pumpkin, etc.). Growers are advised to actively scout for the disease and initiate preventative sprays in watermelon and other cucurbits due to recent reports. The disease is favored by humidity so its critical to have preventive sprays out during rainy or cool temperature periods. The Cucurbit Downy Mildew factsheet, previous alerts, North Carolina fungicide efficacy trials, and The Southeastern US Vegetable Crop Handbook provide recommendations for chemical control options. To prevent fungicide resistance it is critical that growers alternate products in their fungicide programs and tank-mix with a protectant with every application.

If you think you have downy mildew in your field, please contact your local Extension agent and send photos and/or physical samples to the Plant Disease and Insect Clinic. Reporting the occurrence of cucurbit downy mildew to the CDM IPM pipe helps us protect our state’s cucurbit industry by providing them with timely disease management information.

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