Downy mildew has been reported in southern Ontario and MSU Extension is letting growers know that if they haven’t already, it’s time to prepare for the disease.

Caused by Oomycete parasites, downy mildew gets its name from the fluffy sporulation that usually appears on the bottom of infected leaves as the pathogen completes its disease cycle. The spores can germinate and spread the disease to healthy plant tissues. The initial symptoms are chlorotic lesions, which later become brown and necrotic. Cool, wet conditions with high humidity favor disease development.

Though downy mildew affects many crops, cucurbits are particularly susceptible. Syngenta recommends preventive applications of Orondis® Opti fungicide for excellent control of downy mildew and as a resistance management tool.

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