Perennial canker of apple and pear
Pezicula perennans (Kienholz) Nannf.
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.
Uncommon in the east, but has been reported in Canada, Michigan, and some New England states.
Can be confused with other cankers such as those associated with white rot and black rot. The presence of callus rings, associated with older cankers, helps to differentiate perennial canker from white and black rot cankers.
While pesticide applications reduce the spread of cankers and their associated diseases, they are not effective at eradicating existing cankers. It is better to prevent canker establishment by removing existing cankers and following good horticultural practices.
The MSU IPM Program maintains this site as an access point to pest management information at MSU. The IPM Program is administered within the Department of Entomology, fueled by research from the AgBioResearch, delivered to citizens through MSU Extension, and proud to be a part of Project GREEEN.