PORTLAND – A potato virus confirmed last month in Maine has been identified in eight other states, and the Canadian government is imposing import restrictions to prevent its spread, officials said Monday.

Effective on Wednesday, the Canadian Food Inspection Agency is stopping the shipment of seed potatoes from the nine states and placing restrictions on the import of other potatoes to protect against the mop-top virus.

The news surprised U.S. growers who thought they were dealing with one confirmed case and another suspected case, both in Maine.

So far, the Canadian agency has discovered mop-top virus in samples of potatoes imported from California, Florida, Idaho, Maine, Maryland, North Carolina, Oregon, Virginia and Washington, said spokesman Francois Mercure.

“We’re not talking about shutting down the borders. These are interim measures. We are working in cooperation with the United States. We’re trying not to overreact,” Mercure said from Ottawa.

The mop-top virus, which is harmless to people, produces rings of discoloration inside the potatoes, making them unmarketable. The virus can survive for more than 10 years in contaminated fields.

While the U.S. Department of Agriculture was investigating the discoveries in Maine, the Canadian government disclosed late last week that it had been testing imported potatoes since the winter of 2001.

Tests of 2,500 truckloads of potatoes yielded positive test results in 115 samples from the nine states, Mercure said.

The USDA’s Animal and Plant Health Inspection Service is working to verify the Canadian test results and to determine any protocols that must be put in place, said spokeswoman Meghan Thomas.

As of Monday, the USDA still had confirmed only one case at the University of Maine Aroostook Research Farm in Presque Isle. Officials were awaiting laboratory results on the second case, Thomas said.

The discovery by the Canadian government has broad implications. In 2000, more than one-quarter of all U.S. potato exports were fresh potatoes and seed potatoes sold to Canada, according to the National Potato Council.

The affected states include the top U.S. potato producer, Idaho, and four other states that are among the top 10 potato producers.

Interim measures adopted by the Canadian government require potatoes destined for supermarkets from the nine states to be only the highest quality grade and to be treated with a sprout inhibitor, Mercure said.

Potatoes shipped from those states to Canada for processing must be imported under a compliance agreement, he said.

The agreement between the processing plant and the Canadian government would ensure that soil and peelings are disposed of properly and that the trucks were washed to avoid further contamination, he said.

The decision to ban seed potatoes altogether, pending an agreement on a certification program, has no immediate impact because seed potatoes are not shipped at this time of year.

The virus gets its name because the aboveground portion of infected potatoes has an unruly appearance like the mop-top hairdo.

In Canada, it has been found in eight or nine backyard gardens but never on a commercial farm, Mercure said. It already has been discovered elsewhere in Europe, parts of Asia, and South and Central America.

As of now, USDA regulations require a quarantine for a field where mop-top has been discovered. But Maine farmers hope the prevalence of the virus will spur the USDA to drop the quarantine and manage mop-top like other viruses and diseases, said Donald Flannery, executive director of the Maine Potato Board.

Flannery also suggested that the USDA should begin testing potato imports from Canada for the mop-top virus.

Two years ago, the United States closed its border to potatoes from Prince Edward Island after potato wart was found in one field in the Canadian province. The Canadian farmers accused U.S. officials of using the virus as an excuse for protectionism.

The experience is still fresh in the minds of farmers on both sides of the border, said Ned Porter, Maine’s deputy commissioner for agriculture.

“To what extent politics will weigh in, I don’t know. I’d be naive to think that decisions will be science-based only. Politicians don’t work in a vacuum, either state or federal or provincial,” he said.

Mercure offered assurances that the Canadian government would do only what was necessary to protect Canadian growers.

“We’re trying to adopt the science-based approach. We think that at this point and time that those measures are science-based and sufficient to protect the Canadian agriculture,” Mercure said.