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Cherry Leaf Spot

Cherry leaf spot, AKA "shot hole disease" and "yellow leaf" is a destructive infection caused by the fungus Blumerilla jaapii (formerly called Coccomyces hiemali). It affects both sweet and tart cherries and infection is possible from petal fall until after harvest.

Symptoms

Spotted or shot-holed leaves, defoliation; small, flavorless fruits.

Organic Treatments

Raking dead leaves and mowing them in fall is the easiest way to control cherry leaf spot and reduce overwintering spores. As ever, well-pruned trees have good airflow and are less susceptible to infection, as are trees planted in sites with good drainage and plenty of sunlight and airflow. Applications of fungicide may be necessary. Unfortunately, no resistant varieties have been developed yet, but research is underway. Sulfur can be used, but must be applied frequently.

Conventional Treatments

Bravo, Fontellis, and Indar are effective on leaf spot.

Disease Cycle

Cherry leaf spot, AKA "shot hole disease" and "yellow leaf" is a destructive infection caused by the fungus Blumerilla jaapii (formerly called Coccomyces hiemali). It affects both sweet and tart cherries and infection is possible from petal fall until after harvest. The fungus overwinters in diseased leaves on the ground, and around the time of bloom, active spores (ascospores) are released and airborn to young leaves. Initial infection may be minimal, but fresh spores are formed on young leaves within 10-15 days, and these are spread by rain to new sites. Each subsequent wave of infection will become heavier.

The symptoms of cherry leaf spot are small, circular spots on leaves. Initially red-purple, they will develop a brown center with a pale outer ring. The center may drop out to create a "shot hole" appearance, and leaves will turn yellow and drop prematurely. During wet periods, white spores will be visible on the undersides of the spots. Severe defoliation (leaf loss) can weaken the tree, making it susceptible to other infections and winter damage. The fruit of a heavily infected tree will be small, pale, and low in sugar. Ultimately, this disease can kill a tree.

For more information, see the Cornell IPM Fact Sheet on Cherry Leaf Spot and the Cornell Guide to Growing Fruit at Home.






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