Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/23/2002
Publication Date: N/A
Interpretive Summary: During the summer of 2001, a new disease of ash trees broke out in nurseries in Michigan. This disease causes a characteristic canker and has been named coin canker. A fungus was isolated from both the advancing margin of the canker and from the mass of spores that develop in the center of the canker. These isolates were examined and subjected to DNA analysis. It was determined that the fungus that causes coin canker of ash trees is the same as the fungus that causes a disease of apple trees and occurs on many other hosts in North America and around the world. This fungus is reported for the first time on ash trees. This report will alert extension agents and plant quarantine officials to the existence of a new host for this fungus.
Technical Abstract: A serious canker disease of cultivated ash trees in Michigan was determined to be caused by the coelomycetous fungus, Phlyctema vagabunda Desm. (teleomorph: Neofabraea alba (E.J. Guthrie) Verkley = Pezicula alba E.J. Guthrie) (1). Four to five year old trees of Fraxinus americana and F. pennsylvanica had smooth, round, brownish-yellow, cankers about 2-4 cm diam with distinct reddish, cracked margins. Immersed, eventually erumpent, unilocular acervuli develop in the central portions of these cankers. The same fungus was isolated both from the conidia as well as from the margin of the canker. Phlyctema vagabunda has been studied primarily as the cause of Bull's eye canker of apple (2). Using both the ITS and beta tubulin sequences, the fungus from ash was determined to be Phlyctema vagabunda when compared to sequences from apple (2). Phlyctema vagabunda under its numerous synonyms has been reported on various hardwood and herbaceous hosts from temperate regions around the world including the United States but has not been reported previously on species of Fraxinus. A specimen and culture from the ash canker in Michigan has been deposited at BPI 841384 and CBS respectively.