Walnut-Sized Galls on Pin Oak Branches: Twig Galls, Not Tree Killers

Walnut-sized woody balls on pin oak twigs are horned or gouty oak galls (caused by cynipid wasps). Unlike leaf galls, heavy twig gall infestations can weaken or kill branches, but rarely the whole tree.

Management

• Prune and destroy galled twigs when small (early spring).
• Rake fallen leaves.
• Fertilize: 1 lb 10-10-10 per inch trunk diameter, watered in.
• Insecticides rarely effective due to timing difficulty.

Trees usually outgrow the problem with good care.