Occurrence of Potato Wart Caused by Synchytrium endobioticum on Prince Edward Island, Canada.

During harvest (October 2000) of a 26-ha field of processing potatoes (cv. Russet Burbank) on Prince Edward Island (PEI), a small number of tubers with symptoms of potato wart were found in a 1-ha area of the field. Resting sporangia of Synchytrium endobioticum were present in diseased tissue. Potato wart is not endemic in Canada outside of Newfoundland, where the disease has occurred since 1909, and has been under official quarantine control since 1912 (1). In the United States, the disease was eradicated from Pennsylvania and West Virginia by 1974 and, more recently, was eradicated from Maryland, where its presence had been reconfirmed in 1987 (2). Anecdotal information pertaining to the PEI field suggests that the source of infection may have been infected tubers from Newfoundland that were grown in this portion of the field many years ago. Cv. Russet Burbank is resistant to pathotype 1 which occurs in the United Kingdom, but is susceptible to pathotype 2, which predominates in Newfoundland (1). A soil survey confirmed the presence of S. endobioticum resting sporangia in the 1-ha area in which the symptomatic tubers were found. Concentrations of sporangia ranged from <1 to 124 sporangium per g of air-dried soil. Resting sporangia of S. endobioticum were not found in soil samples from fields within a 0.8-km radius of the infested field, nearby garden plots, or fields in which the same equipment had been used since 1984. References: (1) M. C. Hampson. Can. J. Plant Pathol. 15:223, 1993. (2) M. L. Putnam and A. B. Sindermann. Am. Potato J. 71:743, 1994.