Fly speck

Flyspeck is a disease of maturing apples, caused by the fungus Zygophiala jamaicensis (also known as Schizothyrium pomi). Spores germinate when temperatures are between 60 and 83 degrees Fahrenheit (15-28 C.) for about 15 days, and relative humidity exceeds 95 percent. Flyspeck apple disease appears on fruits as a series of tiny black dots, typically in groups of 50 or more.

The fungus responsible for flyspeck overwinters on apple twigs, but may be blown in from wild sources or other fruit trees for a period lasting up to two months around bloom time.