(Aug. 20) The mop top potato virus, found on a Maine farm earlier this month, has been found in potatoes from eight other states, including Idaho and Washington, according to a Canadian Food Inspection Agency (CFIA) report.

As a result, Canada is restricting exports of seed potatoes from those states and requiring that potatoes slated for retail markets be treated with a sprout inhibitor.

Canadian inspectors tested potatoes imported from the U.S. in mid-August, then sent their results to laboratories in Europe to confirm the results, said Mitch Murphy, agriculture minister for Prince Edward Island. The tests revealed mop top in potatoes from California, Florida, Idaho, Maine, Maryland, North Carolina, Oregon, Virginia and Washington.

The virus, until this summer found only outside the U.S., primarily in Europe, is not harmful to humans but causes discoloration or rings inside potatoes, rendering them unusable for the fresh and processed markets. It was found at a University of Maine research farm in Presque Isle, the Maine Potato Board, Presque Isle, reported Aug. 3.

One U.S. potato official, Mel Anderson, president of the Idaho Potato Commission, Boise, questioned the integrity of the CFIA tests.

“I don’t know of any sampling protocol they have with our Department of Agriculture,” Anderson said. “You have to use regulatory samples. If they’re randomly sampling, who knows where these potatoes came from? They may not even be Idaho potatoes. They could be Canadian potatoes.”

Murphy said independent verification by a joint team of U.S. and Canadian inspectors, now under way, would “go a long way” toward confirming the CFIA findings. But he defended the methodology of the CFIA tests.

“Obviously, they have some origin verification that allows them to name those nine states,” Murphy said. “It shouldn’t be an issue of denying that the virus is prevalent.”

Anderson said he was skeptical because he has never heard of mop top virus in Idaho potatoes, despite his frequent contact with university pathologists. But he said the effect on Idaho growers would be minimal because the state doesn’t ship many potatoes to Canada. Even so, Anderson said the U.S. should consider retaliatory action.

“What we need to do is embargo their side, if that’s the kind of game they want to play,” Anderson said.

Murphy denied that the Canadian action was revenge for a U.S. ban two years ago on Prince Edward Island potatoes afflicted with potato wart.

“This is not good for the industry across the continent,” Murphy said. “Having been through it, we don’t wish these diseases on anyone. We’re talking about growers on farms trying to support their families.”