GREAT BEND, N.Y. - Each spring, tens of millions of alfalfa snout beetles rise from the soil to continue their slow, methodical march across upstate New York, laying waste to fields of alfalfa in a single growing season.

Now, after 20 years of research, Cornell University scientists have discovered a pair of microscopic, insect-killing worms that prey on the beetle, an invasive species that has infested 500,000 acres in nine North Country counties - nearly 14 percent of the state's cropland - since it was first identified in 1933.

Scientists hope the nematodes will be part of a two-pronged approach to thwart the wingless weevil. Cornell plant breeders also are working to develop a resistant variety of alfalfa.

“They've done the job,” said John Peck, whose 200-year-old family farm in Jefferson County has been the site of Cornell's testing since 1991. “I went from a heavily infested soil to virtually nothing.

“I'm plowing fields now I haven't touched for four or five years and ... they're gone. I'm seeing healthy tap roots like I haven't seen in nearly 20 years,” said Peck, who has been plagued by as many as a million beetles per square acre on his 340-acre farm.

The adult beetles surface in May after laying eggs at the root of the alfalfa plant. The emerging larvae then feed on plant roots.

“With the discovery of these two nematodes, it's a big deal,” said Robert Mungari, director of the Division of Plant Industry at the state Department of Agriculture and Markets. “It will make a significant impact on the ability of growers to deal with this persistent pest.”

In 2006, New York farmers harvested 370,000 acres of alfalfa worth nearly $112.7 million, making it the state's third most valuable crop behind corn and hay. But alfalfa also is vital to the state's $1.5 billion dairy industry.

Most of the state's 6,000 dairy farmers grow their own alfalfa, said Peter Gregg, a spokesman for the New York Farm Bureau. If a farmer had to find another feed for cows, it would likely be soybeans, currently at record prices, he said.

“Certainly for farmers who have experienced an infestation, it has been devastating,” Gregg said.

The alfalfa snout beetle was first reported in North America in 1896 in Oswego, likely deposited from ship ballast. Farmers first reported it as a pest in 1933, about a decade after alfalfa was planted as a forage crop in New York.

From the 1940s, farmers managed the alfalfa snout beetle mostly with poison baits, but in 1963 insecticide residues began showing up in local milk and farmers quit using the baits by 1972.

Chemical spraying was ineffective because only a small portion of the adult population was ever exposed and vulnerable at any one time during the season. The only remaining management option was intensive crop rotation - but the beetles always came back when the alfalfa did.

“The bottom line was this insect could not be controlled by any conventional means,” said Cornell entomologist Elson Shields. “We have known for many years that there are nematodes that attack only soil insects. The first job was to see if we could find ones adapted to northern New York, and were effective.”

The adult beetles and the larvae spend nearly all of their 2-year life cycle in the soil so Shields and his colleagues focused on biological control methods, specifically the use of so-called entomopathogenic nematodes.

Nematodes are the most numerous multi-cellular animals on earth with nearly 20,000 described species. Any handful of soil will contain thousands of the microscopic worms.

Despite dozens of laboratory, greenhouse and field applications, no single species seemed to be able to reduce beetle populations.

“We accidentally stumbled onto the answer,” Shields said. “One of the species is native to the Peck farm. We introduced the second species. We were only looking at the second species when we suddenly realized it was the combination together that caused the collapse.”

“Each alone is not very effective,” he said.

The first worm worked in the soil near the surface, while the other attacked the larvae deeper down.

The spread of the alfalfa snout beetle has been limited to northern New York and parts of the Canadian province of Ontario.

“It's been New York's special little problem ... even though if they were to spread, it could become a huge problem in the Midwest, or any alfalfa growing state,” Shields said.

The U.S. is the largest alfalfa producer in the world with the upper Midwestern states accounting for nearly half of its output. New York ranks 27th nationally in production.

Funding for Cornell's research came from the Northern New York Agricultural Development Program and New York Farm Viability Institute, two farmer-led nonprofit organizations.

There is a catch.

Unlike chemical treatments, the nematodes cannot be commercially mass produced because they have to be adapted to local soil conditions and would have to be replaced every year, not cost effective for a low-value crop like alfalfa, Shields said.

“We basically need wild nematodes that are going to be there in the soil from now on,” he said.

So, Cornell scientists are pushing a homegrown strategy, hoping to get county chapters of Future Farmers of America and local 4-H organizations to raise the beetles as club projects then apply them to surrounding farms. Beginning next year, Cornell will start teaching local farmers how to raise their own nematodes.

The New York Farm Viability Institute is providing funding so that the nematodes can be applied to 72 key fields in four counties over the next two years.

“A field only needs to be applied once to establish wild nematodes. Even if a farmer does nothing else, normal farming practices will move it around to other fields,” Shields said.

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On the Net:

New York State Department of Agriculture and Markets: www.agmkt.state.ny.us

Northern New York Agricultural Development Program: www.nnyagdev.org

New York Farm Viability Institute: www.nyfarmviability.org

AP-ES-03-20-08 1853EDT