Crown Gall (Agrobacterium tumefaciens)

From: Ostry, Michael E.; Wilson, Louis F.; McNabb, Harold S., Jr.; Moore, Lincoln M. 1988. A guide to insect, disease, and animal pests of poplars. Agric. Handb. 677. Washington, DC: U.S. Department of Agriculture. 118 p.

Importance- This bacterium causes unsightly galls on roots, trunks, and branches of infected trees. Galls can disrupt food and water-conducting tissues, resulting in poor growth of young trees. In addition, stems can break at galls, and decay fungi.

Look For: Globular-shaped small galls. Irregular-shaped, deeply fissured growths, later becoming spongy. Bacterial slime in fissures of galls when very humid.

Branch Gall.

Biology- Crown gall is caused by a bacterium that survives in the soil and infects trees through wounds. Insects, rainsplash, soil particles, and puning tools can harbor the bacterium and spread it to other trees and fields. Agrobacterium tumefaciens causes a cancer-like proliferation of cells by disrupting the host plant's DNA. The bacterium can infest the soil when outer cells of galls are sloughed off.

Control: Do not plant in soil infested wiht the bacterium. Do not propagate infected stock. Destroy infected plants. Use care in cultural practices to avoid spreading the bacterium to other fields or plants on equipment. Biological control by a non-gall-forming strain of the bacterium A. radiobacter has been successful in fruit orchards. This material is available commercially for either a preplant dip or for treatment after planting.

Trunk galls.