Mildew on Zucchini Leaves

Mildew can reduce your zucchini plant's yield.

Zucchini plants are famously productive members of home gardens. If your zucchini plants develop a fungal infection, you could lose most of your crop. Powdery mildew and downy mildew on zucchini leaves are serious problems.

Appearance

Powdery mildew begins as white, powdery blotches on zucchini leaves. It can spread to cover entire leaves so they look like they have been dusted with flour. Downy mildew begins with pale yellow or green spots on zucchini leaves. On the underside, wet-looking, dark spores grow, eventually killing that portion of the leaf.

Issues

Powdery mildew is not only unsightly, but it also can reduce the number and size of zucchini your plants produce. Severe cases of downy mildew can completely defoliate a patch of zucchini, ruining your harvest and killing the plants.

Solutions

Placing your plants far enough apart so that they have good air circulation around the leaves reduces the potential for mildew to develop. Preventative fungicides can stop powdery mildew from gaining a foothold on zucchini leaves. If downy mildew develops, mobile systemic fungicides can control it.

References

• Cornell University Vegetable MD Online: Managing Downy Mildew
• UMassAmherst UMass Extension: Cucumber Powdery Mildew