Powdery Mildew (Erysiphe, Uncinula)

From: Ostry, Michael E.; Wilson, Louis F.; McNabb, Harold S., Jr.; Moore, Lincoln M. 1988. A guide to insect, disease, and animal pests of poplars. Agric. Handb. 677. Washington, DC: U.S. Department of Agriculture. 118 p.

Importance- Powdery mildew, although conspicuous at times, is of minor importance. Severely diseased leaves may be distorted. However, infection does little damage except where the appearance of leaves is important.

Look For: Patches of white-gray powder, sometimes with scattered black fruit bodies on leaf surfaces in late summer.

Diseased Leaf.

Biology- Disease is usually most abundant on lower, shaded leaves. Patches of superficial mycellium can enlarge to cover the entire surface of the leaf.

Control:

• Direct control is usually not necessary.
• Apply a fungicide to trees where appearance is important.