Downy Mildew

Last updated: November 18, 2021

What Does Downy Mildew Mean?

Downy mildew is a micro-biotic fungal infection that occurs in cool moist weather and affects many different plants. It is most often recognized by a yellow or faded spotting that appears on the leaves.

Downy mildew is problematic for growers of grapes, squash, or other plants that grow on vines. It mainly occurs during the wet, cool months of autumn and is a particular problem in the northeast United States. It doesn’t overwinter in northern climates, but can in the Gulf and southern states.


Maximum Yield Explains Downy Mildew

Downy mildew should not be confused with powdery mildew, which is another common fungal infection in plants.

Downy mildew most often appears first on older leaves and on the leaf undersides. If left untreated the leaves will eventually brown off and the plant may die.

Initially, a plant infected with downy mildew will develop brown or yellow spots. These lesions will expand and the underside of the leaf will appear water-soaked. During cool, dew-filled autumn nights the disease can spread very rapidly.

In a commercial setting, particularly vineyards, downy mildew can cause serious damage as it results with low yields and poor fruit quality.

Downy mildew can be treated with a commercial fungicide, but many home remedies are available for gardeners. One method is to eliminate the excess moisture feeding the infection by using drip irrigation instead of a sprinkler, or by reducing the humidity in a greenhouse or growroom.


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