Downy Mildew Information

Downy Mildew Information

By Kat Yares, Garden Guides Contributor
mildew on leaf

About Downy Mildew

Downy mildew is a fungus infection that attacks many different vegetables and vine fruits. The infection is often confused with powdery mildew or blue mold. Signs of infection include brownish yellow spots developing on the surface of the upper leaves. The lower leaves beneath this area will show a feathery white or purplish mold, especially during periods of high humidity. Spores, either by contact with another plant or by the wind, spread downy mildew.

Prevention and Control

Planting disease resistant plants and seeds best controls downy mildew. Cultivate around vegetables to reduce the risk of transferring the mold from weeds or other carriers. After the harvest, till under any remaining plant matter to kill off the spores over winter. Copper-based fungicides can work if used as directed on the label, but overuse can lead to toxic poisoning of the soil and killing earthworms and beneficial microbes.

Affected Plants

Grapes, cucumbers, cabbage and hops are the plants most associated with this fungus.


Downy mildew can cause the leaves of the affected plants to whither and die. If the mildew spreads to the fruit, it can cause misshapen, bitter fruits. If the infestation of the fungi is severe, the entire plant and eventually the entire crop can die.

Other Methods of Control

A compost tea can be applied with a sprayer to the affected crop. When watering, especially in humid areas, avoid watering the leafy portion of the plants.

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