What is "sooty mold"

Sooty mold is a collective term for different Ascomycete fungi, which includes many genera, commonly Cladosporium and Alternaria. It grows on plants and their fruit, but also environmental objects, like fences, garden furniture, stones, even cars. The mold benefits from either a sugary exudate produced by the plant or fruit, or if the plant is infested by honeydew-secreting insects or sap suckers.

Sooty mold itself does little if any harm to the plant. Treatment is indicated, when the mold is combined with insect infestation.