UC IPM Home > Homes, Gardens, Landscapes, and Turf > Trees and Shrubs > Diseases

How to Manage Pests

Pests in Gardens and Landscapes

Downy mildew of roses—Peronospora sparsa

Downy mildew causes purplish, red, or dark brown spots on leaves. Leaf undersides are covered with downy fungal growth. Leaves may yellow and drop. The fungus that causes downy mildew on roses produces spores only on living plants. Resistant spores carry the fungus over unfavorable periods. Downy mildew is favored by moist, humid conditions.

Solutions

Prune plants to improve air circulation. Reduce humidity around plants, by using, for instance, drip or low-volume irrigation. Avoid overhead watering. Fungicide applications help prevent damage.

Purplish spots on rose leafPurplish spots on rose leaf

 

 

Statewide IPM Program, Agriculture and Natural Resources, University of California
All contents copyright © 2013 The Regents of the University of California. All rights reserved.

For noncommercial purposes only, any Web site may link directly to this page. FOR ALL OTHER USES or more information, read Legal Notices. Unfortunately, we cannot provide individual solutions to specific pest problems. See our Home page, or in the U.S., contact your local Cooperative Extension office for assistance. /PMG/GARDEN/PLANTS/DISEASES/downymildew.html revised: May 31, 2013. Contact webmaster.