Common Diseases: Downy mildew

Biology

Downy mildew is a fungal disease of tender green tissues including leaves and shoots. Infected leaves show areas of slightly chlorotic to purplish red to dark brown discoloration on the upper surface. A light gray-brown feltlike growth develops on the undersides of infected leaves. Infected tissues become necrotic, and eventually die. Wet, humid conditions favor disease development. Under favorable conditions, the disease can spread quite rapidly, and the entire plant can droop and die. Many vegetables, ornamentals, flowers, and other plants including grapes and cereal crops are susceptible to downy mildew infections.

Management Options

Use Integrated Pest Management (IPM) for successful plant problem management.

Non-chemical Management

Select non-chemical management options as your first choice!

• Destroy infected plants and debris.

Chemical Management

IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides.

Fungicides may be effective in managing downy mildew in certain situations. However, the fungicide must be registered for the host plant. Contact your county extension agent for additional information.

Additional Images