Absence of Potato Spindle Tuber Viroid (PSTVd) in the United States
At the Certification Section meeting of the Potato Association of America held in Seattle on December 2, 1998, seed potato certification personnel reported an absence of PSTVd in seed potato stocks for the past 10 years. However, the North American Plant Protection Organization continues listing PSTVd as an A-2 Quarantine pest in North America. In addition, many seed-importing countries continue to require the United States to test potato seed crops to ensure freedom from PSTVd. Based on this information, fourteen U.S. seed potato certification agencies (Alaska, California, Colorado, Idaho, Maine, Michigan, Minnesota, Montana, Nebraska, New York, North Dakota, Oregon, Washington, and Wisconsin) surveyed all U.S. seed potato growing areas for the presence of PSTVd. The survey included general surveillance which involved searching for the occurrence of PSTVd in state seed potato certification records from 1990 through 2000, and a specific field survey which involved testing selected crops for PSTVd infection by nucleic acid dot blot hybridization during 1999-2001. No PSTVd incidents were documented in any of the state certification records, nor were PSTVd’s detected in the field surveys. U.S. seed potato certification agencies routinely test seed potato stocks for PSTVd at a number of certification levels starting with pre-nuclear in tissue culture, continuing with field-increased seed generations during the growing season and ending with post-harvest grow-out plots. Based on these surveys, PSTVd has been determined not to be present in any of the seed potato growing areas of United States.