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. Chlorine bleach root dips or sprays are not effective as a crown gall protectant.

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.

Common name		Amount/Acre
(trade name)
When choosing a pesticide, consider information relating to environmental impact. Not all registered pesticides are listed. Always read label of product being used.
A.	AGROBACTERIUM TUMEFACIENS (formerly A. RADIOBACTER) K-84#
	(Galltrol)	Label rates
	MODE OF ACTION GROUP NAME (NUMBER1): A biological fungicide.
	COMMENTS: Preventive preplant treatment only.
B.	GALLEX	Label rates
	COMMENTS: For removal of existing galls, apply winter through spring.
#	Acceptable for use on organically grown produce.
1	Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of actions (for more information, see http://www.frac.info/). Fungicides with a different group number are suitable to alternate in a resistance management program. In California, make no more than one application of fungicides with mode of action Group numbers 1, 4, 9, 11, or 17 before rotating to a fungicide with a different mode of action Group number; for fungicides with other Group numbers, make no more than two consecutive applications before rotating to fungicide with a different mode of action Group number.

PUBLICATION

UC IPM Pest Management Guidelines: Almond
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
B. A. Holtz, UC Cooperative Extension, Madera County
Acknowledgment for contributions to Diseases:
B. L. Teviotdale, Kearney Agricultural Center, Parlier

Top of page