The hairy root bacterium causes infected plants to develop abnormally dense clusters of small roots. This root impairment can cause aboveground parts to develop an unhealthy appearance.
Life cycle
When Agrobacterium rhizogenes infects a host, the bacterium transfers some of its genetic material into plant cells. This causes abnormal growth of plant cells and excess production of small roots in dense clusters. The bacterium persists in soil. It can spread in water and infect plants through wounds.
Damage
The hairy root bacterium can infect many broadleaved plants including blueberry, caneberries, fruit and nut trees, and rose. The bacterium causes roots to develop dense clusters of small, abnormal roots. This impairment of roots can cause foliage to yellow. Infected plants may grow slowly and die prematurely.
Solutions
Purchase and plant only high-quality nursery stock from a reputable supplier. Avoid injuring trees and shrubs during transplanting. Where hairy root has been a problem, soil solarization during the hot dry season before planting may reduce the abundance of hairy root bacteria in topsoil and decrease the development of hairy root disease.
Adapted from Pests of Landscape Trees and Shrubs: An Integrated Pest Management Guide, University of California Statewide Integrated Pest Management Program (UC IPM).
