Crown Gall

Crown gall is caused by Agrobacterium tumefaciens, a soil-borne bacterium that exploits wound sites to insert a portion of its own DNA into plant cells. That genetic transfer forces the infected tissue to proliferate into characteristic corky, tumor-like galls ranging from roughly 1 to 4 inches in diameter. Galls form most commonly at the crown (the soil line), on lateral roots, and occasionally on lower stem tissue. The bacterium persists in soil for years after infected plant material is removed, surviving saprophytically on decomposing tissue.

Infection requires a wound, whether from transplanting, cultivation equipment, freeze injury, insect feeding, or graft incompatibility reactions. Moist soils and mild temperatures during the planting window increase bacterial activity and the likelihood of successful infection. The disease is widespread wherever susceptible crops are grown in temperate zones.

On tree fruits and stone fruits, established crown gall typically reduces vigor and shortens productive lifespan rather than killing the tree outright. On cane fruits, particularly black raspberry and blackberry, the outcome is more severe: infected plants often decline and die within a few seasons. Highbush blueberry is also susceptible, though gall development on blueberry tends to be slower.

The single most cost-effective control is starting with certified disease-free nursery stock. No rescue treatment reverses existing galls. For bare-root plantings, preplant dip with Galltrol-A (a biocontrol formulation of Agrobacterium radiobacter K84) has documented efficacy in reducing new infections when applied before planting in known-infested ground. No crown gall resistant rootstocks or scion varieties are identified in current data for this crop set.