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Etiology and Symptomatology of Canker and Dieback Diseases on Highbush Blueberries Caused by Godronia (Fusicoccum) cassandrae and Diaporthe (Phomopsis) vaccinii. D. P. Weingartner, Former Graduate Research Assistant, Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824, Present address of senior author: Agricultural Research Center, Hastings, Florida 32045; E. J. Klos, Professor, Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824. Phytopathology 65:105-110. Accepted for publication 2 August 1974. DOI: 10.1094/Phyto-65-105.

Both Godronia (Fusicoccum) cassandrae and Diaporthe (Phomopsis) vaccinii cause severe canker and dieback diseases of highbush blueberries in Michigan. Godronia canker and dieback was epiphytotic in northern Michigan, whereas Phomopsis canker and dieback was epiphytotic in some Indiana fields and in extreme southern Michigan. Depending upon the field, either or both diseases were epiphytotic in the center of the blueberry production area. Diagnostic symptoms of Godronia canker and dieback on 1-and 2-year-old stems were red-maroon-brown elliptical lesions which were often centered about a leaf scar whereas wilting of otherwise symptomless stems was most often associated with Phomopsis canker and dieback. On stems more than 2 years old, cankers caused by G. cassandrae and P. vaccinii tended to be wide in relation to their length or long, narrow, and often covered with unbroken bark, respectively. Both fungi caused brown discoloration of stem xylem below wilt symptoms. Isolations were necessary to diagnose the cause of dieback on stems older than two years when fruiting structures were not present. Apothecia of G. cassandrae were common in northern Michigan fields in which Godronia canker and dieback was epiphytotic. Perithecia of D. vaccinii were not found.

Additional keywords: Coryneum microstictum, Fusarium sp., Vaccinium corymbosum, stem galls, stem blight.