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DESCRIPTION Adults are black sawflies 2 to 3 mm long. The flat yellowish-white larvae, about 6 mm, are seldom visible. DAMAGE Larvae tunnel between the leaf surfaces, producing irregularly-shaped brown lines or blotches. Leaves of severely affected trees appear scorched by fire. Grey, white and paper birch are most affected. LIFE CYCLE Pupae overwinter 2 to 5 cm below the soil surface. Adults emerge in spring when leaves are half grown. They hover over birch trees, laying one egg per leaf, usually near branch tips. Eggs soon hatch and larvae mine the leaf for 10 to 15 days. Mature larvae then cut a hole through the leaf, drop to the ground where they pupate for 2 to 3 weeks. There are 2 to 4 generations per year. CONTROLS - If practical remove affected leaves by hand. Plant Black,
European or River birch to prevent leafminer damage, as they
rarely feed on these species. - Inspect tips of birch branches for sawflies when leaves are about
half open. If insect is present, applying contact pesticides can
help reduce numbers.
Keep a pest journal for next year including severity of damage,
controls used, and when you first noticed pest. PESTICIDES - Chemical-Malathion at label rates (contact
pesticides). - Alternative-Safer’s Soap, Trounce or Summer Oil at label rates
(contact pesticides).
Product Highlight
Safer's Soap
Insecticidal soap is the safest of all natural based pest controls. Made from naturally occurring plant oils, the soap disrupts the waxy outer skin of soft-bodied insects, causing dehydration and death. Beneficial insects such as ladybugs and praying mantis are hard-bodied and not affected by the soap. Insecticidal Soap is a contact insecticide and has no residual activity.
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