Cucumber Downy Mildew Confirmed in Wilson County

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Cucurbit downy mildew was reported this week in commercial cucumber fields in Wilson County. Symptoms were typical of downy mildew, including angular chlorotic lesions on the leaves and a grayish-brown “downy” appearance on the abaxial sImage of Cucurbit downy mildewurface. Leaves presented approximately 10% disease severity, but only 5% of the field was affected (Figure 1).

Figure 1: Early downy mildew symptoms on a cucumber leaf (Photo Dr. Lina Quesada-Ocampo, NC State University Vegetable Pathology Lab)

Growers are recommended to take immediate action to protect cucurbit crops in North Carolina, especially since we are experiencing favorable weather conditions for disease. Cucumbers and melons are generally more susceptible to the disease than squash and pumpkin. The pathogen quickly becomes resistant to fungicides especially in cucumber, thus, tank mixing fungicides specific for downy mildew with a protectant fungicide and alternative modes of action is strongly recommended. Effective fungicides and information can be found in our Cucurbit Downy Mildew fact sheet.

We also encourage commercial growers and homeowners to be diligent in checking cucurbit leaves for downy mildew and reporting the disease to the Cucurbit downy mildew IPM pipe website (CDM ipmPIPE). These reports are anonymous and crucial in warning growers throughout the east coast of an outbreak. You can also register to receive texts, emails and/or phone alerts when new disease outbreaks are reported.

If you think you have cucurbit downy mildew, please contact your local Extension Agent and send photos and/or physical samples to the Plant Disease and Insect Clinic.

Be sure to follow NC State Extension Vegetable Pathology reports on Twitter and Facebook for more veggie disease alerts.