Sooty Blotch and Flyspeck Sooty Blotch and Flyspeck Jim Travis, Jo Rytter and Ken Hickey 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. These blotches can be removed by rubbing vigorously and are olive-green to black. 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.