WSU Extension

Hortsense

Apple : Burrknot
(revision date: 5/20/2014)


Biology
Burrknot of apples is a physiological problem which appears as a growth somewhat resembling crown gall. The roughened, warty-looking growth is comprised of root tissues. If buried with soil, burrknots may produce normal roots. Several apple varieties grown in western Washington are susceptible to this problem. High humidity, cool weather, and low light levels are environmental conditions which contribute to the problem. On some varieties grown in western Washington, the symptoms commonly occur on branches or may appear at or just above the soil line. In other areas, severe burrknot problems can cause trees to become stunted, girdled, or weakened at the site of the knot.
Management Options

Non-Chemical Management
  • None recommended
Select non-chemical management options as your first choice!

Chemical Management

None recommended

Images
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Caption: Apple burrknot
Photo by: C.R. Foss
Caption: Apple burrknot
Photo by: C.R. Foss