Crown gall identification & organic treatment
Agrobacterium tumefaciens
How to identify crown gall
A soil bacterium that inserts a piece of its own DNA into the plant's cells at wound sites, tricking the plant into growing rough, woody tumor-like galls, most often at the crown or graft union.
Symptoms
- Rough, woody, irregularly round galls at the base of the stem, crown, or roots, ranging from pea- to fist-sized
- Galls are soft and light-colored when young, becoming hard and dark with age
- Reduced vigor, stunted growth, and decline, especially on younger plants
- Galls often form at graft unions or pruning/planting wounds
Host crops
Apple, Grape, Raspberry, Blueberry.
How it spreads
Lives in soil for years; enters through fresh wounds (planting, pruning, cultivation, frost cracks, grafting); spreads on contaminated tools, irrigation water, and infected nursery stock.
Favorable conditions
Any soil where the bacterium is present combined with fresh wounding; wet, heavy soils and repeated cultivation injury raise risk.
Progression
- Wound infection (Any wounding event near soil bacteria) — Bacteria enter through a fresh cut or crack.
- Gall formation (Weeks to months) — Soft galls form and enlarge at the infection site.
- Decline (Over seasons, if galls girdle vascular tissue) — Reduced vigor, dieback, or plant death in severe cases.
Organic treatment for crown gall
- 1. Remove severely galled plants · high effort
Dig out and destroy plants with large girdling galls; the bacterium persists in soil, so avoid replanting the same susceptible species there.
When: At diagnosis
- 2. Excise small, accessible galls · medium effort
On woody plants, cut out small galls with a clean, disinfected blade well into healthy wood, then disinfect the wound.
When: Dormant season
Prevention
- Buy certified gall-free nursery stock; inspect roots and crowns before planting.
- Avoid wounding crowns and roots during cultivation.
- Disinfect grafting and pruning tools between plants.
- Avoid replanting the same susceptible species in soil with a gall history for several years.
Easy to confuse with
Normal callus tissue at a graft union (smooth, not rough/tumorous), Root-knot nematode galls (smaller, on fine roots, not at the crown).