A Technical Report from The Bartlett Tree Research Laboratories
Olive knot is caused by a bacteria that produces a plant growth hormone (indoleacetic acid, IAA) which causes the olive to produce galls or knots that consist of woody olive-derived tissue. The pathogen can live inside of galls and/or as a surface epiphyte on branch and leaf tissue. Infection by the pathogen occurs at wound sites, and pathogen activity peaks during rain events, when bacteria can be observed oozing from knots. Winter infections are common, but the most important infection period is during spring rains.