Cucurbit downy mildew found on cucumber field in New Jersey
Organic growers should scout their cucurbit plantings on a regular basis and apply an OMRI-approved copper based fungicide or other labeled product to help suppress the development of cucurbit downy mildew. Adequate and repeated spray coverage of the bottom of all leaf surfaces is critical for the control of cucurbit downy mildew in organic cucurbit production. It is important to remember that control of downy mildew begins with planting resistant cucumber varieties when possible. No other cucurbits have resistance to downy mildew.
Source; Rutgers Cooperative Extension