Birch leafminer

On birch leaves you will notice pale or brownish blotch mines starting in early summer, with translucent larva visible inside if held to light. Infested leaves may drop by midsummer if mining is severe, creating patchy defoliation. Look for this damage on paper birch and other Betula species beginning late May.

Rake and destroy fallen leaves in autumn to eliminate pupae before spring emergence; this breaks lifecycle and reduces next year's population significantly. Prune back new growth in June if miners appear, encouraging replacement foliage. Parasitoid wasps naturally suppress populations; avoid insecticides that kill beneficials. Cosmetic damage; trees recover and produce new foliage by late summer.