Downy mildew was confirmed last weekend in Bay County, Michigan. As a result, growers on Michigan’s east side should consider preventive fungicide sprays for cucumbers and melons (watermelons, cantaloupe, muskmelon).
A young downy mildew infection was detected on July 9, 2016, in a commercial cucumber field near harvest, according to a recent report from Mary Hausbeck, Michigan State University Extension, Department of Plant, Soil and Microbial Sciences. It is probable that other cucurbit fields in Bay County and surrounding areas may also be infected with the downy mildew pathogen.
Hausbeck suggests growers on the west side of the state remain vigilant and scout their fields for downy mildew.
Rescue or last-minute fungicide applications fail to limit downy mildew and protect the crop, and several fungicides are no longer effective as a result of pathogen resistance, she says. Field trials show that an infection that is not effectively managed causes yield loss and fruit distortion. Plants must be protected preventively and the timing of the fungicide applications are crucial, especially when weather conditions are favorable for the disease.
“Each year my team evaluates fungicide active ingredients and programs,” Hausbeck says. “Fungicides that have just one downy mildew active ingredient should be tank-mixed with a general protectant fungicide such as Bravo WeatherStik (chlorothalonil, Syngenta) or mancozeb.