Cucumber downy mildew was confirmed on July 21, 2026, from a commercial cucumber sample collected in Lenoir County on July 20. This is the first confirmed report of cucurbit downy mildew in North Carolina during the 2026 growing season. Growers should immediately intensify scouting and transition cucumber fungicide programs to products with strong activity against downy mildew.
This report is on cucumbers which are most commonly affected by clade 2 isolates. A cucumber report does not necessarily indicate an equivalent immediate risk to watermelon, squash, or pumpkin, which are more commonly affected by clade 1 isolates.
See NC State Factsheet on Downy Mildew for more information and pictures.
What Growers Should Do Now
- Scout cucumber fields at least twice weekly, focusing on older leaves and field edges subject to shading.
- Look for angular yellow lesions on the upper leaf surface and gray-purple sporulation on the lower surface during humid mornings.
- Immediately transition from protectant-only programs to fungicides with strong activity against downy mildew (See Table Below).
- Maintain 5–7 day spray intervals during favorable disease conditions.
- Rotate among FRAC groups and follow all label restrictions.
- Current rain and storm patterns are likely to enhance dispersal of the pathogen across the region.
- The occurrence of downy mildew in 2026 is later than in previous years, probably due to dry weather and low pressure in the eastern U.S. region.
Symptoms and Diagnosis
Downy mildew, caused by Pseudoperonospora cubensis, produces pale green to yellow angular lesions restricted by veins on the upper leaf surface. Under humid conditions, gray to dark-purple sporulation develops on the underside of leaves. Microscopic examination reveals branched sporangiophores bearing lemon-shaped sporangia.
