PORTLAND – The U.S. Department of Agriculture announced Wednesday that a national survey of seed potatoes will be conducted before any decisions are made on regulations to control the “mop-top” virus.

The survey, to be completed by year’s end, will cover every certified seed lot in the United States, said Meghan Thomas, spokeswoman for the USDA’s Animal and Plant Health Inspection Service.

All told, there will be 3,000 potatoes tested in each of the 17 states that produce certified seed potatoes, she said.

Results of the survey in the United States and tests being conducted by the Canadian government will form the basis for any future regulatory action that may be taken, Thomas said from Maryland.

Mop-top was confirmed for the first time in the United States in August at the University of Maine Aroostook Research Farm in Presque Isle. It was later confirmed at a second site in northern Maine.

U.S. growers’ hopes that it was an isolated problem were dashed when Canadian officials disclosed that the virus had been found in more than 100 potato samples from eight U.S. states during an 18-month period.

The virus is harmless to people, but produces rings of discoloration inside potatoes, making them unmarketable.

The soil-borne virus can survive for more than 10 years in contaminated fields, and it can lead to yield reductions of 20 percent in some types of potatoes, scientists say.

“We need to do this survey and get it done quickly. Once the survey is done, we will know clearly the frequency of occurrence and where it occurs,” said John Keeling, executive director of the National Potato Council.

States included in the new survey of seed potatoes are Maine, New York, Pennsylvania, Michigan, Wisconsin, Minnesota, Alaska, North Dakota, South Dakota, Nebraska, Montana, Idaho, Washington, Oregon, California, Colorado and Utah.

Those states account for the bulk of U.S. potato production, which was 44.5 billion pounds in 2001, Keeling said.

Keeling said he hopes the Canadian government will conduct similar tests to determine if mop-top exists on commercial farms.

Canadian officials, who say mop-top has been found only in a few backyard gardens in their country, are currently working with U.S. officials to trace the source of infected U.S. potatoes.

But a spokesman for the Canadian Food Inspection Agency left open the door for a similar survey of Canadian farms.

“From our perspective, we’re probably looking at a similar approach” to the U.S. officials, said Alain Boucher, a seed potato specialist for the Canadian agency based in Moncton, New Brunswick.

For now, Canada has stopped seed potato shipments and has placed restrictions on other potatoes from eight states.

If U.S. officials are successful in tracing the original infected shipments to specific farms, then Canada will loosen its restrictions to cover only those fields with mop-top, Boucher said.