Ash Leaf Roller on Green Ash: Cosmetic Damage, Minimal Harm

35-year-old green ash in Calgary shows most leaves folded/rolled but green; unrolled leaves reveal wheat-like structures inside.

Identification

Ash leaf roller moth—native to eastern US/Canada, in prairies since 1999. Caterpillars mine leaves, then roll leaflets into cones for feeding. Adults emerge mid-July. Cold winters limit establishment.

Impact

Leaves remain green and functional despite rolling. Tree appears thinner but photosynthesis continues. Natural parasites (wasps) control populations. Pesticides ineffective—caterpillars protected inside rolls.

Management

No spraying needed. Fertilize with 10-10-10 at 1 lb/inch trunk diameter to compensate for reduced leaf area. Let natural controls work.