Downy Mildew found in SC

From Clemson Plant Pathologist Dr. Tony Keinath:

The first SC report of cucurbit downy mildew this year came on June 6 from a crop consultant, who found it on cucumbers in Bamberg County. Growers should spray all cucumber and cantaloupe crops to prevent or manage downy mildew. The cheapest downy mildew fungicide is Ranman. It can be tank-mixed with chlorothalonil, mancozeb, or tebuconazole to add protection against fungal leaf spots, like gummy stem blight and anthracnose, that will start to spread with the rain. Another option is Orondis Opti, a pre-mix of Orondis and Bravo (chlorothalonil). Watermelon growers should be spraying with protectants, as downy mildew has been spotted on watermelon in south Georgia.

Downy mildew lesions on cucumber leaf. Note how they are delineated by the veins in the leaf. Photo from Dr. Tony Keinath.

For more info on downy mildew management in cucurbit crops, refer to this fact sheet.

Testing What Controls Downy Mildew in Cucumbers – and What Doesn’t

From Clemson Plant Pathologist, Dr. Tony Keinath.

Small growers can manage downy mildew on slicing cucumber and increase yields by growing a partially resistant cultivar, like Bristol, and spraying weekly with moderate-cost fungicides, like chlorothalonil rotated with Ranman. Trellising doesn’t help manage downy mildew. Read Dr. Keinath’s full article about testing cultural and chemical controls for downy mildew here.

The cucumbers ‘Speedway’ (front) and ‘Bristol’ (back) in non-trellised plots with foliage yellowing due to downy mildew on June 23, 2017. Photo by Anthony P. Keinath