How to Manage Pests
UC Pest Management Guidelines
Pathogen: Agrobacterium vitis
In this Guideline:
Gall formation is the typical symptom of this disease. Galls may be produced on canes, trunks, roots, and cordons and may grow to several inches in diameter. Internally, galls are soft and have the appearance of disorganized tissue.
COMMENTS ON THE DISEASE
Agrobacterium vitis is systemic in grapevine wood and plant material that does not appear to be diseased may be infected. The pathogen can exist in living and dead vine debris buried in the soil where it can survive for several years and be an inoculum source causing new vines to become infected. Galls develop at wound sites. These include disbudding sites on rootstocks, sites where suckers have been removed and where the vine has been cut and a field graft made. Gall formation may push the bud shield or graft union off the vine. Injuries caused by cultivation or pruning may result in gall formation. Infected vines may have galls on roots caused by the cracking of woody root tissue during growth. Galls frequently appear where the vine tissue has been damaged by freezing temperatures, thus vineyard site plays a role disease severity. Galls may girdle the vine and disrupt the flow of nutrients, thus restricting vine growth.
Crown gall can be difficult to control. Site selection is critical in growing regions with temperatures near or below freezing; maximizing air drainage will reduce freeze injuries. Avoid injurious practices previously described. Plant vines in sites with no history of crown gall. Current efforts to eliminate the bacterium from vines generated using micro-shoot tip propagation techniques have produced inconsistent results. Certified vines may be infected or may become infected once the vine is planted in the field. In areas where winter injury to the vines occurs, disease incidence will be high if the vines are infected. Grow tubes left on young vines over the winter may increase the incidence of crown gall in infected vines. Chemical treatments are not effective. Currently available products only treat the symptoms and do not eliminate the bacterial infection.
UC IPM Pest Management Guidelines:
R. J. Smith, UC Cooperative Extension, Sonoma County
Acknowledgment for contributions to Diseases:G. M. Leavitt, UC Cooperative Extension, Madera County
A. H. Purcell, Environmental Science, Policy and Management, UC Berkeley
J. J. Stapleton, UC IPM Program, Kearney Agricultural Research Center, Parlier
L. G. Varela, UC IPM Program, Sonoma County
S. Vasquez, UC Cooperative Extension, Fresno County