Birch Leafminers are tiny, black sawflies (wasps). Their entire lifecycle, from adult Leafminers to eggs, larvae, and pupae, takes from 6-8 weeks.
Birch Leafminer Damage
The Birch Leafminer lays its eggs in spring, when young birch leaves are unfolding. The larvae burrow into the leaves, then feed on the tissue from inside the leaf.
Leafminer larvae are very flat, and, stay protected inside the leaf as they feed. As they mature, they emerge from the surface of the leaf, fall to the ground, pupate, then re-emerge as adult Sawflies, repeating the cycle two times per year.
Leafminer infestation is easily recognized by the tunnels and blotches that appear in the birch leaves. Infested leaves turn brown, giving the overall tree a scorched/blighted look. Birch Leafminer infestations are often mistaken as disease.
Where Birch Leaf Miners Are Found Geographically
Birch Leafminers are common in the northern half of the United States and east of the Rockies. They are particularly damaging in the Midwest.
Related or Similar Pests
Elm Leafminer. European Alder Leafminer.