Perennial canker of apple and pear
Disease
Perennial canker of apple and pear
Pezicula perennans (Kienholz) Nannf.
Distribution: Uncommon in the east, but has been reported in Canada, Michigan, and some New England states.
Branch lesions are elliptical, sunken, and orange, purple, or brown in color. A raised layer of callus tissue forms around the infected tissue to isolate the diseased tissue. This occurs year after year as the fungus continues to invade healthy tissue, resulting in a series of concentric callus rings (A). Acervuli are produced in the most recently colonized tissue and appear as small, raised black bodies. The woolly apple aphid (Eriosoma lanigerum) can be found invading these cankers in regions where they both exist.