|Powdery Mildew on USDA 61-1-X|
Powdery mildew is caused by the fungus, Microsphaera alni, which can actually infect both leaves and nuts. Leaf infections are rare in our region but when they occur, cause no economic damage. If nuts are infected soon after pollination, powdery mildew can cause nut drop, reduce nut size or inhibit kernel fill. However, late season infections seem to have little or no impact on nut production. The pecans pictured in the photo were infected by powdery mildew in late July. They should grow to normal size and produce full kernels.
Powdery mildew is often controlled by fungicide applications aimed at controlling pecan scab. In most cases, powdery mildew does not cause enough crop loss to justify the expense of additional fungicide applications specifically aimed at controlling this disease.