Is your maple tree dropping lots of leaves?
June 1, 2007 - Author: Dave Smitley, Michigan State University Extension, Department of Entomology
Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.
Early June is when maple petiole borer larvae finish feeding in the petioles of maple leaves, causing the blackened, restricted petiole (leaf stems) to break and the leaf to fall. The stems usually break at a darkened area near the leaf blade. Usually, infestations are limited to sugar maples and only about 25 to 30 percent or less of the leaves fall to the ground. While spectacular, the leaf drop has little effect on tree health. Sometimes spring storms also cause some maple leaves to drop. The best way to tell is to look at where the leaves came from. If you can still see a small petiole stub attached to the tree, it was most likely due to maple petiole borer. However, if the petiole broke cleanly at the base where it is attached to the tree, it was probably due to wind damage. (view images)