Powdery Mildew on a Zucchini Plant

Foliage diseases, such as powdery mildew and downy mildew, plague zucchini plants around the world. Powdery mildew is a fungal infection caused by an airborne spore. It is most severe in hot, humid areas.

Identification

• Plants affected by powdery mildew will develop white spots on their upper and lower leaves that look like talcum powder. The affected leaves will eventually wilt and turn yellowish. The infection can also spread to the blossoms and the fruit.

Prevention/Solution

• The most common and least expensive preventative treatment is to make a solution of 1 percent baking soda and 1 percent horticultural oil, which encourages the baking soda to stick to plant leaves, in water. Spray the solution on the plant every two weeks.

Treating Powdery Mildew

• If you do get powdery mildew, cut off any affected leaves and burn them. Spray the plant with one of three treatments: a commercial fungicide, a solution of 10 percent garlic and 90 percent water, or a mixture of equal parts milk and water.