How to Manage Pests

UC Pest Management Guidelines

SYMPTOMS

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. They enter only through wounds. Crown gall is most damaging to young trees, either in the nursery or new orchard plantings. Peach-almond hybrid rootstocks are more susceptible to crown gall than Nemaguard rootstocks.

MANAGEMENT

Crown gall is best prevented by purchase of trees from a reputable nursery accompanied by careful handling to avoid injury as much as possible, both during planting and during the life of the tree in the orchard. Preplant treatment is for prevention only. Galltrol is a preparation of the biological control agent Agrobacterium radiobacter-84. It is effective only as a preventive treatment and is used as a root dip or spray before heeling in or planting. It does not eradicate existing galls.

Strains of A. tumefaciens resistant to Galltrol and Norbac have been reported. Their occurrence is not widespread, but failure to control crown gall with these materials should be reported. Eradication involves removal of existing galls and topical application of Gallex. Carefully follow label instructions for exposing crown and roots and removing large galls.

PUBLICATION

UC IPM Pest Management Guidelines: Almonds
UC ANR Publication 3431
Diseases
W. D. Gubler, Plant Pathology, UC Davis
J. E. Adaskaveg, Plant Pathology, UC Riverside
Roger Duncan, UC Cooperative Extension, Stanislaus County
J. J. Stapleton, UC IPM Program, Kearney Agricultural Center
Acknowledgment for contributions to the disease section:
B. L. Teviotdale, Kearney Agricultural Center, Parlier

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