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Leaf Spot (on Photinia)

How can I treat leaf spot on my photinia?

Symptoms(:)

Leaf spots on photinia first appear as minute, slightly raised dots on either surface of the leaf. Older spots have a slightly depressed center with raised margins, see photos in reference.

Cause(s):

The fungus over winters as mycelium in fallen infected leaves from the previous year. In the spring the fungus produces spores that are dispersed by splashing water to healthy tissue. Symptoms first appear on the new growth of the lowest branches and spread gradually upward. The fungus continues to sporulate throughout the growing season. Because the fungus preferentially infects tender, new growth, cultural practices that stimulate succulent growth, such as summer pruning or frequent pruning or fertilization, favor disease.

Control(s):

Collect fallen leaves in the winter to reduce sources of fungal inoculums before new growth appears in the spring. Plants pruned in late summer may suffer infections on resultant new growth into the fall. Avoid frequent pruning and summer fertilization, which stimulate succulent growth.

Reference(s):