Diagnosing Mildews on Vegetables

May 13, 2018

Credit LSU AgCenter

Nothing more frustrating than fruits of labor lost to disease and pests. Though the spring has been pleasant, warm days and cool nights contribute to the growth and spread of many diseases that can attack the vegetables in our gardens.

If you have vegetables such as cucumbers, squash, zucchini, and melons, then you might notice fuzzy white material growing on the leaves and growing to spread. Two types of mildews affect vegetables: downy mildew and powdery mildew. Powdery mildew grows during hot and dry weather. Downy mildews thrive in cool, wet periods.

Powdery mildew will appear as white, powdery spots on both sides of the leaf's surface. It will expand as the infection grows. The leaves will eventually turn yellow or brown and fall off, exposing the plant or the fruit to sunburn.

Downy mildew causes light green to yellow angular spots on the top surface of the foliage. A white fluffy growth will begin to appear on the lower spot of these angular spots. These lesions turn brown and dry up eventually. This mildew progresses from older leaves to newer leaves.