Cucumber plant photos taken by Cornell Vegetable Specialist Elizabeth Buck.

Cucumber plant photos taken by Cornell Vegetable Specialist Elizabeth Buck

2021 Cucurbit Downy Mildew Warning

JAMESTOWN, NEW YORK (July 30, 2021) Cornell Cooperative Extension Vegetable Program warns “Cucurbit Downey Mildew is present in neighboring counties and is expected it to be found soon in Chautauqua County and Pennsylvania.” CDM (cucurbit downy mildew) causes rectangular checkerboarding that stays within the boundaries of veins. Given the current weather patterns, there is high risk that the disease will continue to spread moving on rainstorms. People raising cucumber, melon, pumpkin, and squash should scout their fields twice a week. Professional growers should be implementing their downy mildew best management practices at this time. Many growers throughout the county have received updates and support for managing downy mildew by subscribing to CCE’s VegEdge Newsletter.

Suspected cases of should be put into a zip seal baggie with a big breath of air or spritz of water and left on the counter overnight to force sporulation. Once sporulating, CDM can be visually confirmed by Cornell Cooperative Extension. Unfortunately, they are not great mitigation options once the plants are infected, specifically for homeowners, as most home remedies and off-the-shelf fungicide products do little to stop an infection. Luckily, resistant varieties are available and are a great choice for planting in home gardens next year! CCE is looking to collect samples to provide to researchers who are continuing to work on better controls cucurbit downy mildew. Every gardener can help! To learn more about the disease and see photos and tips for identification please visit

Cornell’s Vegetable specialist are looking to collect a few samples from Chautauqua County. If you suspect that you have CDM, please contact us immediately. Home Gardeners should reach out to the Chautauqua County master gardeners at, 716-664-9502 Ext.224, or email Vegetable producers may contact the CCE Executive Director at, 716-664-9502, Ext. 201 please leave a message including your name, farm location and species affected. We need to track the disease to help protect other farms by knowing where it has moved to and helping you to get your outbreak to stop sporulating.

More details, photos and a Reference chart of fungicides used for CDM control, are available on the CCE Website

The Cornell Vegetable Program is one of many programs offered by Cornell Cooperative Extension of Chautauqua County (CCE-Chautauqua). CCE-Chautauqua is a subordinate governmental agency with an educational mission that operates under a form of organization and administration approved by Cornell University as agent for the State of New York. It is tax-exempt under section 501(c)(3) of the Internal Revenue Code. The association is part of the national cooperative extension system, an educational partnership between County, State, and Federal governments. As New York’s land grant university Cornell administers the system in this state. Each Cornell Cooperative Extension association is an independent employer that is governed by an elected Board of Directors with general oversight from Cornell. All associations work to meet the needs of the counties in which they are located as well as state and national goals. For more information, call 716-664-9502 or visit our website at Cornell University Cooperative Extension provides equal program and employment opportunities.


Elizabeth Buck
Extension Vegetable Specialist

Last updated July 30, 2021