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Defend Your Cucumbers against the Threat of Downy Mildew

August 29, 2019
A photo of a cucumber leaf with downy mildew spots.

Michigan State University Extension has reported downy mildew on cucumbers across the Upper Midwest region, especially MI. We urge growers to take action against this disease to combat any detrimental effects to your marketable yield.

Downy mildew is an Oomycete disease that is one of the most destructive foliar diseases on cucumbers. This pathogen thrives in wet, humid weather, which allows downy mildew to quickly reproduce and spread through air currents, rain, fog or dew.

The most noticeable symptoms of downy mildew are angular lesions on leaves, which usually develop 3-12 days after infection. These lesions first appear pale green, but turn yellow-to-brown as the disease continues to spread and the tissues die. If the leaves are stunted enough, this could cause yield reduction or even plant death. On the underside of the leaves, lesions appear water-soaked and masses of fluffy, purple-gray pathogen spores develop.

It is important to apply fungicides sooner rather than later to protect against the growing threat of downy mildew. We recommend using Orondis® Opti fungicide, which combines 2 modes of action that are highly active against Oomycete diseases, including downy mildew. With built-in resistance management and excellent rainfastness, Orondis Opti gives you increased protection from downy mildew when used as part of a disease control program.

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