Leaf Spot

Brown or purple circular spots appear on leaves in early summer, often starting on older foliage and spreading rapidly in wet weather. The spots enlarge quickly, and the leaf tissue dies from the center outward. On some hosts like cherry, you'll see a distinctive shothole effect where the dead tissue drops out entirely. Yellow halos or a green-island effect, where healthy tissue stays green while the rest yellows, are common signs. Heavy rain and overhead irrigation throughout spring amplify the problem.

Leaf spot diseases matter because early defoliation weakens trees and shrubs, reduces flowering the following year, and can girdle fruit stems causing fruit drop. Your best defense is eliminating conditions that favor the fungi: rake and destroy fallen leaves in autumn to eliminate overwintering spores, improve air circulation through pruning and proper spacing, and avoid wetting foliage with overhead irrigation. In severe cases, fungicide sprays starting at bud break help, but prevention through cultural practices works best in the wet PNW climate.