White Oak Leaf Galls: Wasp Diversity, No Health Threat

Two Gall Types

Tiny white balls on leaf undersides: Multiple wasp species (Cynipidae). Egg-laying chemical expands leaf cells into protective balls.
Concave cup structures: Different wasp species; same mechanism.

Host specificity. Each wasp species targets specific oak species. Red oaks have their own gall wasps.

None needed. 1,700+ gall midge/wasp species in US; impossible to target. Natural enemies (parasitic wasps, birds) regulate populations.

Maryland Forest Service, Montgomery Co.: 301-854-6060. Pest Management: fpm@mda.state.md.us, 410-841-5922. They can ID specific gall wasp if desired.

Galls look alarming but are ecologically fascinating and tree-benign. Enjoy the biodiversity.

Plant Diseases: White Oak Progressive Branch Dieback: Internal Decay Suspected; White Oak Suckering and Gall Wasps: Normal Self-Pruning, Galls Cosmetic—Imidacloprid Ineffective; Red Oak Oozing Dark Fluid: Bacterial Wetwood (Slime Flux); Horned Oak Galls on Pin Oak: Same Pest, Same Approach; White Oak Leafless Branches: Natural Shedding or Concern?; Black Oak Sudden Oak Death or Slime Flux in California Mountains; Calandiva Disease Diagnosis: Bacterial Leaf Spot, Insect Damage, and Home Remedies; White Oak Leaf Galls: Wool Sower Gall Identification; Oak Galls: Species-Specific, Not a Health Threat; Louisiana vs. Texas Live Oaks: Understanding the Differences

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