46 Rose Gardening: powdery mildew:
Description
This article is from the Rose Gardening FAQ, by Bill Chandler chandler@austin.ibm.com, Jolene Adams jolene@cchem.berkeley.edu, Brent C. Dickerson odinthor@csulf.edu, Karen Baldwin kbaldwin@veribest.com, and many contributors
46 Rose Gardening: powdery mildew:
This fungus forms a powdery white or grayish coating on the upper surface of
young leaves and sometimes on the buds. Infected leaves crumple and become
distorted.
Unlike blackspot, wet conditions actually inhibit the development of powdery
mildew. It can not reproduce in water. It thrives during high humidity but
forms on dry leaves. Warm dry days, cool dry nights are ideal for powdery
mildew.
One of the best ways to avoid powdery mildew is to keep things as airy as
possible. Roses planted too close to a wall may not get enough airflow.
Prune away crossing canes and open the center of the bush to allow sunlight
and airflow.
Also, spraying the foliage with a mixture of 1 T. baking soda per 1 gallon
of water can be effective.
See blackspot for other treatments of powdery mildew.
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