Burrknot

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.