Rose: Downy mildew
categories: Flowers Ornamentals Rose Rose Diseases
last review date: 2025-07-28 11:02
Photo by: R.S. Byther
Biology
Downy mildew can affect leaves, stems, flower stems, and flower parts. The infection is usually found only on young growth.
On leaves, symptoms include purplish or brown spots, usually between veins, and yellow leaves with green spots. Infected leaves may drop off the plant.
Grayish fungal masses may be found on the underside of some infected leaves (unlike powdery mildew, which is white and found on both sides of leaves).
Symptoms on stems and flower parts can include small or large purple to black spots.
Small, infected twigs can be killed.
Management Options
Use Integrated Pest Management (IPM) for successful problem management.
Non-chemical Management
Select non-chemical management options as your first choice!
- Plant varieties that are less susceptible to the disease.
- Collect and destroy all fallen leaves from beneath plants.
- Prune and destroy all infected portions of plants.
- Space plantings and prune to provide good air circulation.
- Avoid overhead watering to help reduce humidity around plants.
Chemical Management
IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides.
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Focus on cultural control.
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Copper fungicides may have some efficacy, but may cause discoloration of foliage or blooms.
Approved Pesticides
Examples of pesticides that are legal for home use in Washington State are listed below.
The list may not include all products registered for this use.
WSU Extension programs and employment are available to all without discrimination.
Evidence of noncompliance may be reported through your local Extension office.