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Crown Gall

Agrobacterium tumefaciens

Author: Esther McGinnis

Symptoms

  • Crown gall is caused by a soil-borne bacterium that enters tree wounds caused by mower damage, pruning, frost cracks, insects or planting damage.
  • The bacteria stimulate the tree to produce plant hormones that cause a tumor or gall to form.
  • The galls most commonly occur on the roots or on the trunk near the soil line.
  • At first, the galls appear light-colored and spongy.
  • As the galls mature, they turn dark brown and woody.

Figure 1. Crown Gall
Figure 1
: Crown gall frequently appears near the soil line. (Bruce Watt, University of Maine, Bugwood.org)

Figure 2. Crown Gall
Figure 2
: Crown gall can enter through pruning wounds. (Manfred Mielke, U.S. Department of Agriculture Forest Service, Bugwood.org)

Management and other important facts

  • No cure exists for the disease, and it may kill a young apple tree by girdling the stem.
  • A mature apple tree may be able to tolerate crown gall.
  • Carefully inspect apple trees to avoid purchasing a tree infected with crown gall.
  • If a recently planted tree develops crown gall, remove the tree and adjacent soil; the bacteria can persist for several years in the soil.
  • If your property has a history of crown gall infections, avoid planting fruit trees or other susceptible plants.

 

This website was supported by the U.S. Department of Agriculture’s (USDA) Agricultural Marketing Service through grant 14-SCBGP-ND-0038.
Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the USDA.

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