Raspberry root gall

The causal agent of raspberry root gall is the soil-borne bacterium Rhizobium rubi, formerly known as Agrobacterium rubi. This pathogen belongs to a group of bacteria that cause tumorous growths on the roots and crowns of various plants. The infection occurs when bacteria enter plant tissues through wounds created during cultivation, transplanting, or by soil-dwelling pests.

The primary hosts for this disease are raspberries and blackberries. The pathogen is remarkably persistent, capable of surviving in the soil for several years. This longevity makes it a persistent challenge for commercial fruit growers and home gardeners alike, as the bacterium can survive in plant debris and soil particles long after the infected host has been removed.

The most prominent symptoms of Rhizobium rubi infection are spherical or irregular galls found on the roots, crown, or lower stem of the canes. These galls start as soft, light-colored swellings but eventually harden and turn dark brown or black. As the galls grow, they disrupt the plant's vascular system, leading to stunted growth, leaf chlorosis, and a drastic reduction in fruit yield.

Favorable conditions for the spread of the disease include high soil temperatures and moisture. The bacterium is most commonly introduced into new areas via infected nursery stock. Once established, it can be spread across a field through contaminated pruning tools, runoff water, or the movement of soil during mechanical cultivation and weeding.

There is currently no chemical treatment to cure plants once they are infected with root gall. Management strategies must focus on strict prevention: source only disease-free, certified planting material, practice proper crop rotation, and sanitize tools thoroughly between plants. If an infected plant is discovered, it must be removed entirely, including the root system, and destroyed by burning to prevent further spread.