Crown gall

Crown gall is a widespread plant disease caused by the soil-borne bacterium Agrobacterium tumefaciens. This pathogen is unique because it transfers a segment of its own DNA into the plant cell, inducing the formation of tumors or galls, which serve as a nutrient source for the bacteria.

This infection affects a wide variety of plants, including ornamental shrubs, fruit trees, and berry crops. The disease is particularly problematic in raspberry (Rubus idaeus) plantations, where it severely compromises plant vigor and crop quality.

The primary symptom is the development of spongy, light-colored, or white galls on the crown (the area between the stem and roots) or directly on the root system. As these galls mature, they become dark, woody, and necrotic. These structures disrupt the vascular system, preventing water and nutrient transport throughout the plant.

The pathogen thrives in temperate climates and spreads most easily through wounds caused by pruning, grafting, or feeding by soil pests like nematodes. It can persist in the soil for several years, making it difficult to eradicate once a site is infested with the bacterium.

Management focuses strictly on sanitation and prevention. This includes sourcing certified disease-free planting stock, avoiding planting in soil known to be contaminated, and ensuring that garden tools are sterilized with appropriate disinfectants after working on suspect plants to prevent cross-contamination.