WSU Extension

Hortsense

Apple
 
Disease
Anthracnose and Bull's-eye rot 
Bitter pit 
Burrknot 
Crown and collar rot 
Crown gall 
Cytospora canker 
Fire blight 
Fruit russeting 
Nectria canker (European canker) 
Nectria twig blight (Coral spot) 
Perennial canker (Bull's-eye rot) 
Phytophthora fruit rot 
Powdery mildew 
Scab 
Virus diseases 
Insect
Aphids 
Apple ermine moth 
Apple maggot 
Apple-and-thorn skeletonizer 
Brown marmorated stink bug 
Codling moth 
Cutworms and armyworms 
Earwigs 
Fruittree leafroller 
Leafhoppers 
Leafrollers 
Lecanium scale 
San Jose scale 
Spider mites 
Tent caterpillars 
Tentiform leafminer 



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