burrknot
Image:Apple tree burrknot, A2, side.jpgBurrknot is a tree disorder caused by the formation of adventitious root primordia. Although previously classified as disease, is now classified as a disorder, as it is no longer believed to be pathogenic.{{cite web|first=Václav|last=Kůdela|title=Bradavčitá uzlovitost na kmenech jabloně|work=online article|publisher=ZahradaWeb.cz|accessdate=2011-11-19|url=http://www.zahradaweb.cz/informace-z-oboru/ovocnarska-vyroba/Bradavcita-uzlovitost-na-kmenech-jablone__s513x44852.html|archive-url=https://web.archive.org/web/20120404034451/http://www.zahradaweb.cz/informace-z-oboru/ovocnarska-vyroba/Bradavcita-uzlovitost-na-kmenech-jablone__s513x44852.html|url-status=dead|archive-date=2012-04-04}}
It first looks like a smooth orange bulge growing from the stem or a branch. Later, multiple adventitious roots form.{{Citation needed|date=December 2024}}
Description
The occurrence of Burrknot is quite common among rootstock, often found on apple tree M ( Malling ) and MM ( Malling-Merton ) rootstocks.{{cite web|last=cummins|first=steve|title=THE CORNELL-GENEVA ROOTSTOCKS|work=online article|publisher=cummins nursery}} At onset it begins to look like a smooth orange bulge growing from the stem or a branch, later, during one to three years, multiple adventitious roots begin to form.
When located on the roots, it is considered to be not very dangerous, but it makes it easier for diseases to infect the tree, and leaves it more susceptible to insects.{{cite web|author1=Pfeiffer, Killian |author2=Biddinger, Hull |title=Burr Knot Borers|url=http://www.virginiafruit.ento.vt.edu/burrknot.html|work=Online Reprint|publisher=NRAES|accessdate=2011-11-19}} When many burrknots are present on various location in the tree, it can make the tree unproductive.{{cite web|last=Roos|first=Debbie|title=Apple Problem|url=http://www.ces.ncsu.edu/chatham/ag/SustAg/burrknot.html|work=online database|publisher=Chatham County Center|accessdate=2011-11-19}}
Treatment
It is recommended to protect trees from moisture and shadow at the burrknot location, and to prevent infestation by synanthedon myopaeformis.
Similar diseases and disorders
A disease somewhat similar in appearance is a crown gall.{{cn|date=December 2023}}