Oak gall wasp
50 host plants
Last updated
You will observe various gall types on oak leaves and twigs depending on species present. Large apple-like galls up to five inches appear on Garry oak branches; mustard-seed-sized jumping galls form on leaf undersides and drop in fall; mottled spherical galls reach one inch diameter on leaf surfaces. Most galls appear in summer and persist through winter. Oak gall wasps are common throughout Puget Sound oaks.
Galls are primarily cosmetic and cause no apparent damage to tree health. Branch-girdling galls sometimes require removal for appearance. Hand-pick jumping galls if they are excessive nuisance indoors. No chemical control is justified. Resist treatment; galls provide valuable food for wildlife.