How to Manage Pests

UC Pest Management Guidelines

SYMPTOMS

Crown gall appears as rough, abnormal galls on roots or trunk. Galls are soft and spongy. The centers of older galls decay. Young trees become stunted; older trees often develop secondary wood rots.

COMMENTS ON THE DISEASE

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 peach rootstocks are susceptible to crown gall.

MANAGEMENT

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 peach orchard, it is usually best to tolerate the problem for the few remaining years of orchard life, which is about 12 to 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.

PUBLICATION

UC IPM Pest Management Guidelines: Peach
UC ANR Publication 3454
Diseases
W. D. Gubler, Plant Pathology, UC Davis
J. E. Adaskaveg, Plant Pathology, UC Riverside
J. K. Hasey, UC Cooperative Extension, Sutter/Yuba counties
Acknowledgment for contributions to the diseases section:
B. L. Teviotdale, Kearney Agricultural Center, Parlier

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