How to Manage Pests

UC Pest Management Guidelines

COMMENTS ON THE DISEASE
A wide variety of both woody and herbaceous plants are susceptible. The disease is most damaging to trees because the galls are perennial and increase in size with growth of the tree. Galls may occur on roots, stems, and even leaves. Aerial galls are common on grapes and berries. Under moist conditions aerial galls are often seen on chrysanthemum.

Gall tissue is disorganized with an enlarged cambium layer and irregular vascular tissue. Movement of water and nutrients is severely impaired by galls. The early stages of gall formation can be difficult to distinguish from normal callus tissue. Isolation of the pathogenic bacterium is the most common method of confirming that the bacterium is present. Callus tissue, which is soft and easily wounded, can be a common site of infection.

The bacterium Agrobacterium tumefaciens is common in many agricultural soils. When the plant is wounded, the bacterium attaches to an exposed plant cell and transfers a portion of its genetic material, DNA (deoxyribonucleic acid), into the cell where it is incorporated into the genetic material of the host cell. The host cell is induced to become a tumor cell and also to produce a unique substance (opine) that only the crown gall bacterium can readily utilize. Agrobacterium tumefaciens is then able to multiply between cells and in cracks of the gall with somewhat less competition from other microorganisms.

MANAGEMENT
The only certain method of eliminating the bacterium from soil is heat treatment. The common soil fumigants reduce the population of bacteria but do not control the pathogen.

Sanitation is very important in a control program, especially where cuttings are produced. Rose propagative material and work areas are often soaked or cleaned with hypochlorite solution to kill any bacteria that may be present on the surface. Grape propagative material and perhaps some others have also been treated in this manner. In some plants, such as grape, the bacterium may occasionally enter the xylem. Cuttings taken from such plants may develop crown galls.

Tools and surfaces that contact the propagative material should be cleaned and periodically treated with a disinfectant.

CONTROL
An excellent biological control agent, Agrobacterium tumefaciens, is available for use in preventing infection by the crown gall pathogen.

Galls on many woody plants can be treated with a mixture of chemicals that are toxic to and kill crown gall tissue but are safe on uninfected woody tissue. The mixture, which is currently marketed under the name Gallex, was previously sold as Bacticin. It has been used with success on rose crown galls.

Common name
(trade name)		Amount to Use
A.	AGROBACTERIUM TUMEFACIENS K-84
	(Galltrol)	Label rates
	...OR...
	AGROBACTERIUM RADIOBACTER (Strain K1026)
	(Nogall)	Label rates
	COMMENTS: Prevents infection by the crown gall pathogen if it is applied to fresh wounds. It must be applied as soon as possible after wounding; i.e., within 24 hours. It has been used with success on Prunus spp. and Rosa spp.
B.	GALLEX	Label rates
	COMMENTS: For killing of existing galls; apply directly to galls winter through spring.

PUBLICATION

UC IPM Pest Management Guidelines: Floriculture and Ornamental Nurseries
UC ANR Publication 3392
Diseases
R. D. Raabe (emeritus), Environmental Science, Policy, and Management (ESPM), UC Berkeley
M. E. Grebus, Plant Pathology, UC Riverside
C. A. Wilen, UC IPM Program, UC Cooperative Extension, San Diego Co.
A. H. McCain (emeritus), Environmental Science, Policy, and Management (ESPM), UC Berkeley

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