Microthyriella rubi Petr.
Flyspeck is an orchard disease of apples that occasionally is found on the market in shipments originating from the humid growing sections of the country. The superficial blemishes produced by this disease reduce the value of affected fruits on the market. Often, on the same fruit, flyspeck will appear together with sooty blotch, another superficial disease.
Flyspeck appears as small, slightly raised, black specks on the fruit surface (top photo). The specks are fungal growths that commonly occur in groups of 8 to 50 or more and are seldom found singly. Infrequently, an irregular distribution of the specks may occur on the fruits. While the specks can be scraped off easily, they are not usually removed in normal handling operations.
The causal fungus, Microthyriella rubi, is active only in cool, humid weather. Flyspeck commonly develops on maturing apples in orchards located in low lands, in sites with poor air drainage, and in regions where fogs are frequent. The disease is most likely to occur where spray schedules have not been followed.
Spray applications will control flyspeck. The recommendations of the State agricultural experiment station or extension service should be followed regarding choice of spray materials and the spray schedule.
Flyspeck, Golden Delicious