The water mold cucurbit downy mildew affects cucurbits (vine crops in the squash family) every year, especially in summer and fall. Downy mildew spreads quickly on cucumber, muskmelon, and watermelon. Prevention before it appears and prompt action afterward are needed to manage this aggressive disease. Outbreaks of cucurbit downy mildew are most likely during mild, wet weather. Rain washes spores out of the air onto leaves. Rain, dew, or fog makes infection likely. After infection, downy mildew will continue to spread, even in dry weather, if temperatures are above 60°F.
