Oak Branch Galls and Insects in Houston

The "knots" on your 5-year-old oak branches with white webbing and holes inside are likely gall wasps (cynipids) or gall midges. The white webbing may be from secondary spider occupants or fungal growth.

Gall Insects on Oak

• Hundreds of species; each forms a distinct gall shape.
• Larvae develop inside, protected; adults emerge later.
• Most are cosmetic only—they don't harm tree health unless extremely numerous.

Action Steps

1. Do not spray—gall makers are protected inside; sprays kill beneficials.
2. Prune out heavily galled twigs if unsightly (dispose of them).
3. Contact Texas A&M Forest Service (Mickey Merritt or Dallas Singleton) for free ID and advice. They know local oak gall species.

When to Worry

If galls are on main trunk, cause significant dieback, or tree shows overall decline, get an arborist evaluation. Otherwise, galls are just part of oak ecology.