Purple plum trees (Prunus cerasifera), also called cherry plums, are fruiting trees belonging to the Rosaceae plant family. Purple plum trees often suffer from plant diseases that cause holes to form in the leaves.
Shot hole disease and bacterial spot often cause purple plum tree leaves to develop distinct holes.
The Pseudomonas syringae bacteria cause shot hole disease. Bacterial spot is triggered by the Xanthomonas pruni pathogens.
Shot hole disease and bacterial spot initially cause water-soaked lesions to appear on the undersides of purple plum tree leaves. These lesions turn brown or dark purple as the disease matures.
The center of the lesions fall out of the infected leaves, leaving behind holes surrounded by red margins. Purple plum tree leaves with numerous holes typically turn yellow and fall off the tree.
Copper fungicides sometimes help control both shot hole disease and bacterial spot. Fallen plum tree leaves and twigs must be raked up and discarded since the disease pathogens overwinter in the debris.
Earwig infestations cause symptoms similar to shot hole disease. Boron toxicity can also cause sections of plum tree leaves to fall out.