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Oak Horned Gall Wasp: Beneficial Insect Architecture

Rebecca: roundish growths with root-like projections on large oak. Thought wasp galls. Doesn't mind hosting but fears tree death. Photo provided.

Oak horned gall

Oak horned gall wasp structures

Expert Identification

Steve: horned oak gall (wasp). Hard, weaken branches when large. Usually no significant impact on mature tree health.

Key Insight

These dramatic structures are wasp nurseries. While they can stress branches, mature oaks tolerate them well. Hosting supports biodiversity without threatening the tree.

Plant Diseases: BB-Sized Bumps on Oak Branches: Galls or Scale? Stress is the Root Cause; Webs Covering Oak Tree—Not Webworms: Spider Mites; Forest Tent Caterpillars Defoliating Oaks in Manitoba; Oak Leaf Galls ("Jumping Beans"): Harmless to Grass, Plants, People; Orange Fuzz Balls on Post Oak: Woolly Leaf Galls; Live Oak Showing Decline: Sprouts on Trunk, Bare Branches; Oak Leaf Galls: Harmless to Children, Just Insect Nurseries; Red Oak Hollow Trunk: Natural Aging, Not Imminent Hazard; Oak Leaf Galls in Coastal Maine; Stopping Live Oak Root Sprouts in Monkey Grass Beds

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