Beetles are skeletonizing my tree's leaves in summer. How do I stop them?

Leaves chewed down to a lacy skeleton in mid-summer, with metallic green-and-copper beetles clustered on them, are the work of Japanese beetles (Popillia japonica). Adults feed on the tissue between leaf veins, leaving the characteristic lace pattern, and favor lindens, crabapples, cherries, birches, and roses.

Life cycle to understand:

• Adults emerge late June through August and feed for 4-6 weeks
• They release aggregation pheromones — a few beetles quickly become a swarm
• Females lay eggs in turf; the grubs feed on grass roots before overwintering

Control that works:

1. Hand-pick in the early morning when beetles are sluggish — knock them into soapy water. On small trees this is surprisingly effective.
2. Skip the pheromone traps — they attract far more beetles to your yard than they catch.
3. Neem oil repels and deters feeding; reapply after rain.
4. For heavy pressure on high-value trees, systemic or contact insecticides can be used, but avoid spraying flowering plants where pollinators forage.
5. Healthy, well-watered trees tolerate considerable defoliation — established trees usually recover fully even after looking ragged.

Grub control in lawns reduces next year's local population somewhat, but adults fly in from elsewhere, so it's not a complete fix.