Powdery Mildew on Zucchini Leaves

Zucchini and cucumbers are at risk for developing powdery mildew.

Do not despair if you find powdery mildew on your zucchini leaves. This common problem can be managed so your plant will produce plenty of zucchini before the growing season ends.

Appearance

Powdery mildew growing on your zucchini leaves will begin as small white patches. As the fungus spreads, it will cover the leaves until it looks as though they have been dusted with flour, according to Dr. Curtis Smith, Extension Horticulture Specialist. The mildew can spread to the zucchini fruit.

Management

Manage powdery mildew on zucchini leaves through careful watering. Water in the morning, and allow the soil and area to dry in between waterings. Make sure plenty of air can circulate around your zucchini plants and expose them to sunlight. Remove any dead or damaged leaves from the plant and from the ground where they fall, according to "Mediterranean Kitchen Garden."

Considerations

Once your infected zucchini plant is done producing for the year, you can remove it from your garden. This will reduce the risk of powdery mildew returning the next year. If you want to use the plant for composting, you need to kill the mildew spores first. Seal it in a clear plastic bag and leave it in full sun for a few days. The heat in the bag will kill the fungus spores and make the plant material safe for you to use.

References

• New Mexico State University: White Blotches On Zucchini Leaves May Be Normal Or May Be Fungus
• "Mediterranean Kitchen Garden"; Mariano Bueno, Evelyn Fitzherbert; 2010