July 30, 1999
Infection by the cherry leaf spot fungus causes small purple leaf spots (up to 3mm) that eventually turn brown. These spots sometimes drop out, causing a shot hole appearance. Affected leaves turn bright yellow and drop prematurely.
The causal fungus, Blumeriella jaapii (once known as Coccomyces hiemalis) may infect sour cherry, sweet cherry, chokecherry, common plum, wild plum, and other Prunus species.
Potted plants propagated as stem cuttings such as impatiens, geraniums, and poinsettia are more susceptible to Rhizoctonia crown and cutting rot. The problem begins right after plants are transplanted in the landscape. The disease starts out as a dry, brown basal rot that can develop before or after rooting. Then the base of stem breaks off easily from the rest of the plant. Affected plants may also suffer from wilting, chlorosis, stunting, and eventually death.
These two insects are similar in appearance and habit and appear at about the same time in Iowa. Both are common "accidental invaders" that crawl into houses and buildings from outdoors by mistake. They are active from mid-July to early August.