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Leafminers are small insects that feed between the layers of tissue in deciduous leaves or feed inside evergreen needles. They can be caterpillars or larvae of flies or wasps.

Aspen blotchminer

Aspens are heavily attacked by the aspen blotchminer. These small caterpillars infest poplars as well as aspen trees.The larvae are flattened and spend their whole life inside the leaf tissue. Adults are very small gray moths.

Spruce needleminer adult or larva

Needles of spruce are mined by this small caterpillar. The greenish or greenish brown larva chews a hole in the base of the needle and then eats the interior of the needle.

Bundle of needles mined by needleminer

Larvae feed from June until the first frost and tie the eaten needles together in these characteristic bundles.

Birch leafminer

The Birch leafminer is the larva of a sawfly that commonly infests gray and paper birch leaves. The larvae are flat and complete development in a couple weeks. New growth is preferred and there can be more than one generation per year.