Late maturing apple and pear cultivars may have sooty blotch and fly speck develop on the fruit surface. Both diseases are favored by moderate temperatures, abundant rainfall, and high humidity. Colonies are mutually exclusive though both diseases normally appear on the same fruit. Sooty blotch results in sooty-like brown to green blotches on the outer skin of the fruit.
Pycnidia are asexual fruiting structures associated with certain fungi.
The fungus is superficial but can only be removed by vigorous rubbing. Flyspeck appears as small, shiny black dots that tend to cluster in groups of a few to about 100 though groups of 10 to 50 are most common. While they appear to be isolated, the dots are connected by a hyphal strand. Both fungi overwinter on twigs of many wild hosts. Sooty blotch conidia are disseminated by wind into orchards from late May or June until fall.