Did you know that there is fungal disease called sooty mold caused by fumago vagans?
This non-pathogenic fungus and several other fungi have been reported including Capnodium elongatum, Echidnodella angustiformis etc that grows on plants surface at areas covered by honeydew (which is a sticky liquid a sugary substance excreted by insects: mealybugs, aphids, mites, scales and caterpillars as they feed on the plants).