Control of the insects will result in a decline in the dark fungus growth and a return to normal green color. Leaves may also drop from insect damage. A short portion of the petiole is still attached to the leaf blade. This affect only a few leaves, does little harm, and generally stops about two weeks after the first drop is observed. Chemical injuries may cause leaves to drop in summer.
Effects depend on the chemical, season, temperature, tree species, etc.
Some chemicals may discolor the leaves which do not drop, while other may result in leaf drop. Other misapplied chemicals could kill the tree. Fallen leaf clusters, attached to short twigs, may result from twig-girdling insect. A shallow depression encircles the broken end of these twigs. This is often spotty damage and does little harm to the plant.