Nut and Foliage Diseases

Powdery Mildew

(fungus Microsphaera alvi)

When pecans become infected with this fungus, they appear to be covered with a white, powdery material. The fungus develops on the outside of the shuck and only feeds on the outer layer of plant cells. Thus, although it appears to be causing considerable damage, no significant yield losses can be attributed to the presence of the fungus. Powdery mildew can develop at very low humidity, and is a problem during the mid-summer months. Once the fall rains begin, the fungus is washed off the shuck leaving only the dead epidermal cells of the shuck.

When the foliage is infected, it becomes slightly distorted and covered with a faint white, powdery substance. Foliage infection is a problem only on the lower, immature leaves of a tree and on nursery trees.

Control is based on following a scab fungicide program with no special sprays. In nurseries where the foliage is all immature, Benlate sprays may be required if mildew begins to develop.

 

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