Oak Galls on Scrub Oak: Woody Twig Galls

Identification

Dark growths on trunks/branches are likely gouty oak gall or horned oak gall—woody masses caused by tiny wasps.

Life Cycle

• Start as leaf blisters in spring.
• Develop into woody twig galls over 1–2 years.
• Adults emerge spring; females lay eggs in leaves.

Control

• Insecticides ineffective (wasps protected inside).
• Prune infested twigs on lightly affected trees.
• Heavy infestation on large trees: impractical to prune.

Outlook

Galls rarely threaten tree health. Monitor; prune if feasible.