Cucumber scouts near Chatham, ON identified downy mildew symptoms in a cucumber field, and it was confirmed by Dr. Cheryl Trueman at the University of Guelph this afternoon.
This is a earliest we have seen downy mildew in a number of years. As the plants in most areas are still very small, many grower will not have started their preventative fungicide programs. Now that the disease has been confirmed in Ontario, fungicides should be applied as soon as possible!
See the article, Cucurbit Downy Mildew – get out and scout! – ONvegetables, for information about fungicide selection.
Given the early start to the 2021 cucurbit downy mildew season, growers and scouts are encouraged to inspect all fields for CDM, regardless of the crop stage. Look for angular “water-soaked” lesions on the older leaves. These lesions are often most noticeable in the morning, and may simply look like the dew has been slow to dry. The angular shape of the lesions is characteristic. Later in the day, new lesions will begin to dry and turn yellow-to-tan. Under humid conditions, grey mildew hyphae with enbedded spores may be visible on the lower leaf surface.
The 2021 downy mildew scouting program is funded by the Ontario Processing Vegetable Growers and is delivered in Kent County by Tomecek Ag Services.