ST. AGATHA – A mere 18 months ago, farmers and other players in northern Maine’s potato industry celebrated the expansion of a french fry plant with the star product on the buffet table.

Demand had soared for three decades, prompting McCain Foods USA to double capacity at its Easton facility. Plans for a second McCain plant were in the works and rival Lamb Weston planned to set up shop in nearby Limestone.

But those plans have been postponed because the skyrocketing growth hit a plateau, leaving processors with a glut of capacity.

It’s disappointing news for farmers who hoped the additional plants would help reverse a downward trend in Maine.

“Aroostook County was on a high for one year because the plants were coming,” said Dan LaBrie, a fourth-generation potato grower from St. Agatha. “I had never seen the industry so upbeat.”

Maine grew more potatoes than any other state before World War II but the state has sunk to eighth place today. Acreage peaked in 1946 when more than 23.5 million tons were harvested from 219,000 acres. That dropped to 800,000 tons harvested from 62,000 acres in 2001.

Over the past two decades, about 800 potato growers gave up their farms as cheaper potatoes from the West and Canada made it harder for Mainers to compete. Today, Maine has about 400 growers.

The American appetite for french fries once seemed insatiable, and that was good news in Maine where half of the remaining acreage is devoted to fries.

But consumption that grew from 4 pounds per person in 1960 to a peak of 30 pounds in 1996 has leveled off in the United States, according to Charles Plummer, an economist with the U.S. Department of Agriculture.

Consumption dropped even more after Sept. 11, as the economy flagged and fewer people ate out, said Don Flannery, executive director of the Maine Potato Board in Presque Isle. Fast food restaurants account for more than 90 percent of sales, according to agriculture officials.

Americans, on average, already eat 140 pounds of potatoes a year, versus 106 pounds four decades ago. But processors hope to get people to eat even more with new variations like jalapeno-flavored fries, a fry-chip hybrid called the “Frip” and smiley-face potatoes for tykes.

The industry also is looking to China, where growing wealth and the expansion of fast food restaurants could help keep U.S. processors busy for at least 20 years, said Rob Russell of the United States Potato Board.

Despite all those efforts, it’s not clear when McCain and Lamb Weston will build their plants in Maine.

“We’re just going to watch as things unfold in the coming months and years, and I can’t give you any clearer answer,” said Frank van Schaayk, president of McCain Foods USA.

Lamb Weston, a subsidiary of ConAgra Foods Inc., relinquished its option to build a french fry plant at Loring Commerce Centre, a former Air Force base that is now a business park.

Brian Hamel, the authority’s president, remains optimistic that the plant will be built sometime in the next two years.

For LaBrie, the plants represented the opportunity to sell a larger percentage of his crop under contracts instead of on the open market.

About 70 percent of his crop already is earmarked for processors.

“The nice thing about doing a contract with a processor is you contract before you plant the crop. So at least you know that you have a market, and you know the conditions of the sale,” LaBrie said. “So, it’s less of a gamble. … I’m not a gambling man.”

But the presence of Lamb Weston would have meant something more as well: another major processor in a state where McCain, the state’s only major french fry maker, buys about 40 percent of the crop.

“How can you put a dollar value on a monopoly versus competition?” asked Vernon DeLong, executive director of the Agricultural Bargaining Council, which negotiates on behalf of Maine growers.

Business is demanding these days, LaBrie said, as growers face tough negotiations with processors, flat demand and increasing competition on top of the other concerns that come along with farming, like the weather.

“Everybody worries, and rightfully so,” he said. “If you can’t change with the times, you’ll be swept away.”