Powdery mildew of apricot, nectarine, peach and plum

Sphaerotheca pannosa (Wallr.:Fr.) Lév. Podosphaera clandestine (Wallr.:Fr.) Lév.

Distribution: Occurs all along the east coast.

Photos

The infection may progress to cover the entire fruit, causing deformity. Mid-Atlantic Orchard Monitoring Guide
C

Infection appears as white circular lesions of patches of powdery growth on either side of the leaf, or on the terminal ends of new shoot growth. Severely infected leaves curl upward or blister, may be stunted, but eventually drop as infection progresses (A). Leaves on new shoots may be narrow, strap-like, and distorted. Except for plum, young foliage is affected by S. pannosa; older foliage is affected by P. clandestine. Infections of the fruit begin with appearance of white, circular spots (B). On young fruit, the infection may progress and cover the entire fruit, causing them to become deformed. On older fruit, the lesions eventually cause the surrounding tissue to become necrotic and scabby; nectarines remain green (C).

Crops Affected: peaches, plums

Management

Powdery mildew is managed through a combination of fungicides, starting from petal fall and continuing through pit hardening, and the use of resistant varieties. Many fungicides used for brown rot control are effective against powdery mildew.