Cherry Leaf Spot or Shothole

By The Old House Web

Cherry Leaf Spot or Shothole

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Cherry leaf spot, or shot hole, caused by the fungus Coccomyces hiemalis, reduces flowering and weakens the tree. Cherry leaf spot often defoliates the tree by midsummer. Repeated defoliation makes the tree more susceptible to winter injury and may eventually kill it.

Symptoms: Leaves show small purple to brown spots with definite boundaries in early summer. The leaves turn yellow and fall. In July, the centers of the infected spots frequently fall out, giving a shot-hole appearance.

Cause: The fungus overwinters on fallen leaves. In spring following wet weather, spores form and winds blow them to infect leaves. When temperatures are favorable (60 to 75 degrees F), infection requires a wet period of only a few hours. Leaves are susceptible when fully unfolded -- this usually occurs near petal fall. The initial leaf infections form spots, and more spores are produced in the spots. These spores are rain splashed to infect other leaves. Secondary spread and infection by spores continues repeatedly, whenever wet warm weather occurs, until leaves fall in autumn.

Control: Rake and burn fallen leaves before spring. Fungicides should be used if plants are prematurely defoliated. Time spray applications beginning at petal fall; continue every 14 days if rain is predicted during the period. If initial infection is controlled, subsequent spray applications are unwarranted.

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