Why Is My Maple Tree Losing Green Leaves?

Identification

• All varieties of maple are susceptible to infestation from the maple petiole borer. The pests are a non-stinging type of wasp resembling small sawflies. The pupae overwinter in the soil. Adults emerge in spring and lay their eggs in the foliage stems.

Damage

• Pest presence is characterized by the sudden loss of foliage between late May and early June. Newly hatched larvae eat into foliage petioles and sever the connective tissues, causing green leaves to drop from the tree. Damaged petioles turn black, while the leaves stay green. Once in the soil, the larvae leave the stems to pupate in the ground.

Control

• Maple petiole borers are hard to control, but since their presence does not seriously jeopardize trees, insecticidal control options are usually not required. Removing fallen leaves from under the tree is not a practical control option either.