Crown gall

Crown gall is a widespread bacterial disease caused by the soil-borne pathogen Agrobacterium tumefaciens. This bacterium infects plants by transferring a specific segment of its DNA into the plant cells, which triggers abnormal, rapid cell division, resulting in the formation of tumor-like growths known as galls.

The host range of this pathogen is remarkably broad, affecting numerous woody and herbaceous species. Notable susceptible plants include Anemone coronaria, fodder beet, winter rapeseed, turnip, Campanula carpatica, hemp, hazelnut, and dahlia.

Symptoms typically manifest as round, spongy, and light-colored galls on the roots or crown of the plant. As the galls age, they turn woody, dark, and irregular in shape. The presence of these tumors disrupts the plant's vascular system, leading to stunted growth, nutrient deficiency symptoms, poor flowering, and increased susceptibility to other stressors.

The development of crown gall is favored by soil temperatures between 15°C and 30°C and high soil moisture. Bacteria enter the plant exclusively through fresh wounds caused by root insects, nematodes, improper cultivation practices, or grafting. Once established in the soil, the bacteria can persist for long periods, making eradication difficult.

Management focuses on preventive measures, as chemical control is generally ineffective once a plant is infected.

• Always use certified, disease-free nursery stock.
• Implement strict sanitation of pruning tools to prevent spread.
• Avoid mechanical damage to roots during transplanting.
• Utilize biological control agents like Agrobacterium radiobacter to protect healthy roots.