Birch Leafminers are small, black sawflies (wasps). The entire lifecycle, from adult Leafminers to eggs, larvae, and pupae, takes from 6-8 weeks.
The Birch Leafminer lays its eggs in the spring, when young birch leaves are emerging. The larvae burrow down into the leaves, where they feed on the tissue from inside the leaf.
Leafminers are incredibly flat, and, as larvae, stay protected inside the leaf. As they mature, they eat their way to the surface of the leaf, fall to the ground, pupate, then emerge as adult Sawflies, repeating the cycle two times per year.
Leafminer infestation is detectable by the tunnels and blotches that appear in the birch leaves. Attacked leaves turn brown, giving affected trees a scorched/blighted look. Birch Leafminer infestations are often misdiagnosed as disease. They prefer gray, paper, white and cut leaf birch.
Birch Leafminers are found in the northern half of the U.S. and east of the Rockies. It is particularly damaging in the Midwest.
Similar or Related Pests
European Alder Leafminer, Elm Leafminer