Downy mildew refers to any of several types of oomycete microbes that are obligate parasites of plants. Downy mildews exclusively belong to Peronosporaceae. In commercial agriculture, they are a particular problem for growers of crucifers, grapes and vegetables that grow on vines.

Problem: Downy mildew is caused by fungus-like organisms and affects many ornamentals and edibles, such as impatiens, pansies, columbine, grapevines, lettuce and cole crops such as broccoli and cauliflower. Often occurring during wet weather, downy mildew causes the upper portion of leaves to discolor, while the bottoms develop white or gray mold.

Solution: Plant resistant cultivars when available. No fungicides are available, but cultural practices can help. Remove and destroy infected foliage, or entire plants if downy mildew is prevalent. Avoid crowding plants or watering them in the evening, and rotate edibles year to year.

Regards

Joseph Mareddy

Assistant Managing Editor

Journal of Plant Biochemistry and physiology