Leaf spot of cherry—Blumeriella jaapii
Leaf spot of cherry foliage is a fungal disease that primarily occurs in coastal areas. During years of high rainfall the disease sometimes occurs at interior locations.
Identification
The fungus Blumeriella jaapii causes irregular lesions to appear on the lower and upper surfaces of infected cherry leaves. Spots may range in color from brown to pale gray, tan, or dark purplish. As an affected leaf dries, tissue may fall out and give the leaf a tattered appearance. Infected leaves turn yellow overall and drop prematurely.
When conditions are humid or leaves are wet, tiny, stringlike tendrils of whitish spores ooze from leaf spots on the underside of leaves. Fruit on affected trees may become spotted and abnormally soft.
Life cycle
The fungus overwinters on leaves dropped beneath trees. During high humidity or wet weather, spores are produced from the leaf lesions and are forcibly ejected and carried by wind to infect leaves on the tree. Leaves are susceptible to infection by the fungus throughout the growing season. The fungus continues to spread anytime infected leaves are wet.
Damage
Leaf spot damages cherry leaves and causes them to drop prematurely. If trees are extensively defoliated before harvest, fruit can become soft and ripen unevenly and fruit yield can be reduced the following growing season.
Solutions
Remove diseased leaves as soon as they appear and dispose of them away from cherry trees because the leaves can be a source of infectious spores. Where cherry leaf spot has been a problem, removing all leaves left on the tree at the end of each growing season and those dropped on the ground may help to reduce the pathogen's abundance the following year. If leaf spot was a problem the previous growing season, spraying sulfur to thoroughly cover all leaves can reduce the subsequent abundance of leaf spot disease.
Adapted from Integrated Pest Management for Stone Fruits, University of California Statewide Integrated Pest Management Program (UC IPM). |
