Leopold Center
U.S. Department of Agriculture



The sooty blotch and flyspeck fungi live on the waxy layer that coats the surface of apple fruits. The fungi include: Zygophiala jamaicensis, the causal agent of flyspeck; and three sooty blotch fungi, P. fructicola, Leptodontium elatius, and Geastrumia polystigmatis.
These fungi live on sugars and other nutrients that leak out of the apple. They also survive and grow on the twigs and branches of many woody plants, including apple, but are especially likely to occur on raspberry and blackberry canes. Spores released in the late spring and summer spread to apple fruits by rain and wind. In the Upper Midwest, the first symptoms of sooty blotch and flyspeck typically appear in late August to early September, but can appear earlier in wet years. On the other hand, sooty blotch and flyspeck symptoms can be rare or even absent in Upper Midwest orchards in years when rainfall is sparse.

Sooty blotch and flyspeck tend to be more visible on light-skinned (yellow or green) than on red apple cultivars, and more severe on late-maturing than early-maturing cultivars.

Click here for pictures of the infected apple.

Email: mgleason@iastate.edu Telephone: (515) 294 0579 Address: 312 Bessey Hall, Iowa State University, Ames IA 50011