Mild Temps, Clouds and Rain = Increased Late Blight, Downy Mildew Risk

Late blight on tomatoes. Photo by Wayne County IPM Scout Chris Smedley.

Late blight has been confirmed on tomatoes in Wayne and Ashland counties this week.  We also found downy mildew in basil, cucumber and melons in our sentinel plots in Fremont and Celeryville, OH. Downy mildew is assumed to be widespread on cucumbers and melons in Ohio, but we have not yet found downy mildew on squash or pumpkins. The late blight and downy mildew pathogens are related and all are favored by moderate temperatures, rain, high humidity and cloudy skies. Tomatoes, potatoes, cucurbits and basil should be scouted regularly and treated with protectant fungicides. Management recommendations have been posted this summer for all of these diseases.  See the following:

Late blight: conventional and organic management

Cucurbit downy mildew management

Basil downy mildew management

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