Concentric rings show the regular advance of this fungus (Cytospora) through the branch. The dark bumps are the fruiting bodies of the fungus.
Photo by Jay W. Pscheidt, 1999.
Corkscrew willow with Phomopsis cankers.
OSU Plant Clinic Image, 2016.
Cankers on this willow were due to Colletotricum.
OSU Plant Clinic Image, 2018.