Oak Crown Gall and Leaf Galls: Different Problems

Your oak has orange/red leaf spots and knotty root growths. Leaf spots = gall wasps; root knots = crown gall (Agrobacterium tumefaciens).

Leaf Galls

• Wasp-induced; cosmetic; no treatment.

Crown Gall

• Bacteria enter wounds → tumor cells form galls.
• Galls range pea-size to >1 ft; woody, rough.
• Interrupt water/nutrient flow; weaken tree.
• No cure. Control = prevention (avoid root/trunk wounds).

Care

• Fertilize fall & spring: 10-10-10 at 1 lb/inch diameter.
• Water deeply in drought.
• Mulch to prevent mower damage.

Bottom Line

Two separate issues. Leaf galls harmless. Crown gall untreatable—maximize health to extend tree life.