How to Manage Pests

UC Pest Management Guidelines

SYMPTOMS

Rough, abnormal galls form on roots or trunk. Galls are not hard but 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.

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 12-15 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.

Common name
(trade name)		Amount to Use
When choosing a pesticide, consider information relating to environmental quality.
A.	AGROBACTERIUM TUMEFACIENS-84#
	(Galltrol)	Label rates
	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.

PUBLICATION

UC IPM Pest Management Guidelines: Plum
UC ANR Publication 3462
Diseases
W. D. Gubler, Plant Pathology, UC Davis
J. E. Adaskaveg, Plant Pathology, UC Riverside
K. R. Day, UC Cooperative Extension, Tulare County
Acknowledgment for contributions to the diseases section:
B. L. Teviotdale, Kearney Agricultural Center, Parlier

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