Sooty blotch and flyspeck affect apple, crabapple, and pear trees. These are separate diseases, but both can be present on the fruit at the same time. They cause only surface blemishes that detract from fruit appearance and also lowers fruit quality and market value. Sooty blotch also shortens fruit storage life because of increased water loss due to this disease. Both diseases, however, are economically important problems, especially on late-maturing cultivars and on scab-resistant cultivars that are grown without fungicides. Sooty blotch is a disease complex and is caused by several unrelated fungi. Flyspeck is caused by the fungus Zygophiala jamaicensis. Sooty blotch appears on fruit surfaces as sooty or cloudy blotches with indefinite boarders. These blotches can be removed by rubbing vigorously and are olive green to black. Flyspeck looks like true "flyspecks" characterized by sharply defined, small, black, shiny dots in groups of a few to nearly 100 or more.

Symptoms

Disease Cycle
Both fungi overwinter on the twigs of many woody plants as well as apple and pear. Spores of the fungi are windblown and rain splashed onto fruit. Infection can occur anytime after petal fall but is most prevalent in mid to late summer. Disease outbreaks are favored by extended periods of above normal summer temperatures combined with frequent rainfall and high humidity. These diseases usually appear on fruit late in the season.

Disease Management

Routine fungicide sprays normally control this disease in Pennsylvania. Cultural controls include the removal of alternate hosts such as wild blackberries from the orchard and surrounding hedgerows. Dormant and summer pruning that opens up the tree canopy and facilitates air movement and the drying of fruit after a rain period will help in the control of these diseases. Thinning to separate the fruit clusters will also help prevent sooty blotch and flyspeck. No cultivar resistance to these diseases is known. Prune trees annually to improve air circulation and reduce the potential for disease. Cool fruit after picking to retard the development of the disease.