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Burrknot

Non-pathogenic (genetic/physiological)

13 host plants

Last updated

Data Coverage 3 of 6 dimensions
Causal Agent
Host Plants
Symptoms
Management
GDD Threshold
Regional Notes

Burrknot develops as rough, warty growths above the soil line on dwarfing apple rootstocks like M9. You see spherical bumps that are actually root initials developing abnormally. The knot can increase in size during the season and potentially girdle the tree. Management includes avoiding rootstocks prone to burrknot, mounding soil, and removing knots.

Avoid using rootstocks genetically disposed to this problem. Mound soil around the base of the tree to encourage the burrknots to root.

Quick Reference

Causal Agent
Non-pathogenic (genetic/physiological)
Host Plants
13

Management

Cultural Controls

  • Avoid using rootstocks genetically disposed to this problem.
  • Mound soil around the base of the tree to encourage the burrknots to root.
  • Plant trees with the graft union 1 to 2 inches above the soil line.
  • However, the risk of scion rooting increases with these soil-related control measures.
  • Remove or kill the tissue with a knife or blowtorch.
  • However, this generally is not an economical alternative.

Host Plants (13)