Why Are Maple Leaves Falling From My Tree?

An unusual, but benign, insect our arborists often cross paths with in the spring in Michigan is the maple petiole borer. This native insect is most often found on younger sugar maple trees. The damage caused by maple petiole borer can cause anxiety with homeowners because soon after the sugar maple leaves fully emerge, they suddenly 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 slender 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 has a relatively low impact on a tree. The insect only produces one generation per year. Most of the time only a small number of leaves fall from the affected sugar 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.

Given the minimal leaf loss and the lack of long-term harm caused by the maple petiole borer, no insect control measures are necessary. Homeowners need not worry, as this insect does not typically cause any significant harm to the tree’s health. If you feel you must take some action then consider a deep-root fertilization for the tree. This will not control maple petiole borer, but it will make sure there are adequate nutrients in the soil for the tree to draw upon when needed.

Wilted leaves in sugar maple caused by maple petiole borer. | Tom Morgan, Owen Tree Service

Fallen sugar maple leaves caused by maple petiole borer. | Tom Morgan, Owen Tree Service