Disease Note

Cytospora Canker on Acer platanoides in Southeastern Michigan. E. T. Smiley, Department of Forestry, Michigan State University, East Lansing 48824. J. J. Kielbaso, and T. J. Proffer, Department of Forestry, Michigan State University, East Lansing 48824. Plant Dis. 69:360. Accepted for publication 9 December 1984. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/PD-69-360f.

During summer 1984, losses of Norway maple (Acer platanoides L.) increased dramatically in the metropolitan Detroit area of Michigan. A survey examining 25% of the 16, 185-tree Norway maple population in Dearborn. Michigan, identified 27.6% as symptomatic. Symptoms ranged from twig dieback to death of the entire tree. Dead branches generally retained their leaves. Bark on dead limbs and trunks rapidly split longitudinally. Cankers were often observed exuding reddish brown fluid. Symptomatic trees were mainly 30–45 cm DBH and 25–35 yr old and had shown reduced growth during the previous 3 yr. Cytospora pycnidia were present on some dead branches. Cytospora sp. was isolated from discolored cambial and xylem tissues in 12 of 18 diseased samples examined in the laboratory. Trees may have been predisposed by two abnormal winters and three summers with extended droughty periods.