Crown Gall
Rhizobium radiobacter (formerly Agrobacterium tumefaciens)
125 host plants · Bacterial
Last updated
Crown gall appears as rough, irregular galls at the base of the plant, at the soil line, or occasionally on roots and aerial branches. Young galls are pale, soft, and almost wart-like; as they age, they become dark and woody with a bumpy, cauliflower-like texture. In some cases, they're smooth enough that you might mistake them for callus tissue from grafting or pruning. Infected plants often show stunted growth, poor foliage color, and reduced flowering. On stone and pome fruits, roses, and blueberries, crown gall can develop slowly, sometimes taking over a year for visible symptoms after initial infection.
Crown gall is caused by a bacterium that enters plants through wounds, whether from pruning, mechanical injury, or natural root emergence. Once inside, the bacterium transfers DNA that transforms normal cells into tumor cells that proliferate uncontrollably. There is no cure; management depends on prevention and sanitation. Purchase only disease-free nursery stock and inspect plants before planting; discard any showing gall symptoms. Avoid wounding plants, especially during planting. Sterilize pruning tools frequently when working around infected plants, as contaminated shears spread bacteria to cut surfaces. Do not plant susceptible crops in previously infested soil for 2-3 years, and do not allow tools or equipment to track infested soil into clean areas. Choose resistant rootstocks when available, particularly for roses.
Quick Reference
Management
Throughout growing season when wounds occur. Symptoms may be delayed >1 year if infection occurs in cold temperatures.
Presence of wounds. Warmer temperatures favor bacterial activity and symptom development.
Cultural Controls
- Purchase pathogen-free nursery stock; inspect all new plants before planting and reject any showing gall symptoms.
- Remove and destroy infected plants immediately.
- Avoid planting in soil with recent history of crown gall infection; if necessary, rotate to non-susceptible crops (grasses, vegetables) for 2-3 years before replanting susceptible species.
- Sterilize pruning tools between cuts, especially when cutting through galls or on infected plants.
- Minimize wounding during planting, pruning, and cultivation.
- Preplant soil solarization may reduce bacterial populations: cover rototilled, irrigation-saturated soil with clear plastic (anti-condensation film preferred) for 4-6 weeks during hottest part of summer (early-mid July onward), burying plastic edges to trap heat.