Cherry leaf spot
Blumeriella jaapi (Rehm) Arx
Lesions begin as small, circular red to purplish spots on the upper leaf surface (A). Spots enlarge as they grow older, typically coalescing and turning brown (B). Lesion centers may eventually drop out to give the leaf a "shot-hole" appearance, particularly on plum. The most striking symptom of cherry leaf spot, especially on sour cherry, is the yellowing of older leaves prior to their falling from the tree (C). When infection is severe, the entire tree may be defoliated by midsummer. Spores are produced on the underside of leaf lesions in acervuli and appear as a white to pinkish mass in the center of the lesion (D).
Common to all fruit-growing regions in eastern North America.
The striking discoloration of the foliage along with the production of acervuli on the underside of leaves helps to distinguish this disease form other foliar diseases, such as bacterial canker.
The disease is managed through the application of fungicides from petal fall and continuing through midsummer. Removal or destruction of fallen leaves will reduce leaf spot pressure the following season because the first infections each spring are caused by inconspicuous apothecia that develop on dead leaves on the ground (E). Sour cherry is most susceptible to the disease; sweet cherry and European plum are affected but less so than sour cherry.
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