Maple Petiole Borer

An unusual, but benign, insect we often cross paths with in the spring in Michigan is the maple petiole borer. The damage caused by maple petiole borers can cause anxiety with homeowners because soon after the maple leaves fully emerge they start falling from the tree.

A close examination of the fallen maple leaves will often reveal a darkened area on the petiole of the leaf. The petiole is the stem that connects the leaf to the tree branch. The maple petiole borer itself remains on the portion of the petiole still attached to the tree so you won’t be able to find the larvae in the leaf petioles on the ground.

The maple petiole borer only produces one generation per year. Most of the time only a small number of leaves fall from the affected maple tree and no significant damage is done. Occasionally, a maple can experience 30-50% leaf loss, but this is highly unusual because parasites generally keep the maple petiole borer population under control. No insect controls are recommended due to the minor amount of leaf loss caused by this insect.