Plum Leaf Spot
Leaf spot of plums and prune-type plums is caused by the fungus Coccomyces prunophorae. The fungus, its life cycle, and the disease it causes are very similar to those of cherry leaf spot. On plum leaves, the spots tend to be smaller, and severely infected leaves often have a tattered appearance. Unlike cherry infection, severe plum leaf infection is often followed by a heavy fruit drop.
Most varieties are susceptible to the disease, so fungicide sprays, along with the sanitation practices suggested for cherry leaf spot, are necessary for control. A light disking should be done just before overwintered spores on leaves are ready to be discharged, about the time of shuck fall.