what type of insect causes leaf drop
A close examination of leaves on the ground will likely show leaves with only a small portion of their stems (petiole). This leaf drop is caused by the feeding of maple petiole borers, Caulocampus acericaulis. Petiole borers are small insects called sawflies, which are non-stinging wasps. The sawfly is only about 1/6 of an inch long and emerges from the soil in the spring to mate and lay eggs near the base of the petiole of maple leaves.
Insect borers often attack trees that are weakened or damaged by other causes. In some cases, borers and plant pathogens are associated with the same canker. Leaf drop Leaf drop is generally caused by plant pathogens or environmental problems.