How to Manage Pests

Pests in Gardens and Landscapes

Crown gall—Agrobacterium tumefaciens

Crown gall hosts include chrysanthemum, dahlia, geranium, marigold, peony, and snapdragon. The crown gall bacterium causes distorted growths or galls, principally on the basal stem and root crown at the soil line or just below the soil surface. Galls sometimes also form on roots, limbs, and trunks of many species of woody plants. Under moist conditions, galls may appear on upper stems or even leaves of some plants. Infected plants may become distorted, grow slowly, and become stressed and susceptible to drought or other problems. Foliage may be chlorotic and leaves may be small.


Sanitation is the most important management strategy for crown gall. Clean tools, containers, and work surfaces frequently and treat them with a commercial disinfectant. Use only high-quality plants. Avoid injuring plants, especially around the soil level and when plants are wet. Dig out and destroy infected plants. In hot areas, solarizing the soil before planting can reduce crown gall bacteria in the soil. Infection may be prevented by dipping cuttings in Agrobacterium tumefaciens K-84, a biological control agent that produces an antibiotic that reduces or eliminates infection.

Distorted trunk growth
Distorted trunk growth on a dying Euonymus plant infected with crown gall

Statewide IPM Program, Agriculture and Natural Resources, University of California
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