Elm leaf beetle

Elm leaf beetle larvae skeletonize American elm leaves in the Puget Sound, leaving a lacy, brown pattern as they consume tissue while veins remain. You will see yellow-green adult beetles with dark spots and a broad stripe along each wing edge feeding on leaves. Larvae are black or black-and-yellow, covered with tiny bumps. Damage appears in spring as larvae feed on new foliage; heavy infestations can defoliate entire trees.

Promote natural parasitoids and predators that control beetle populations. Prune out and destroy infested branches if caught early. Horticultural oil applied in dormancy reduces overwintering beetle numbers. No chemical control is recommended for landscape trees in Western Washington due to low pest pressure. Most elm trees in home gardens tolerate moderate leaf loss without serious harm. Focus management on maintaining tree vigor through proper watering and avoiding unnecessary wounding.