How to Manage Pests
UC Pest Management Guidelines
Pathogen: Agrobacterium tumefaciens
(Reviewed 6/10, updated 6/10, pesticides updated 9/15)
In this Guideline:
Crown gall appears as rough, abnormal galls on roots or trunk. Galls are soft and spongy. The center of older galls decay. Young trees become stunted; older trees often develop secondary wood rots.
The bacteria survive in gall tissue and in soil. Crown gall is most damaging to young trees, either in the nursery or new orchard plantings. All nectarine rootstocks are susceptible to crown gall.
The incidence of crown gall can be reduced by planting noninfected, "clean" trees. It is also important to carefully handle trees to avoid injury as much as possible, both at planting and during the life of the tree in the orchard. Preplant, preventive dips or sprays with a biological control agent are available and may be helpful in some orchards. Generally, by the time crown gall is evident in a nectarine orchard, it is usually best to tolerate the problem for the few remaining years of orchard life, which is about 12-15 years, or just remove the orchard and start anew.
When replanting a previously affected site, remove as many of the old tree roots as possible, grow a grass rotation crop to help degrade leftover host material and reduce pathogen levels, and offset the new trees from the previous tree spacing to minimize contact of healthy new roots with any infested roots that may remain.
UC IPM Pest Management Guidelines: Nectarine
J. E. Adaskaveg, Plant Pathology, UC Riverside
Acknowledgment for contributions to Diseases:B. L. Teviotdale, Kearney Agricultural Center, Parlier
W. D. Gubler, Plant Pathology, UC Davis