PHIPPSBURG – Scientists may have found the ultimate weapon to control the spread of purple loosestrife: a tiny brown beetle.

The bug’s ability to defoliate purple loosestrife could prove critical to the survival of other plants and natural habitat at the 600-acre Morse Mountain Preserve.

Loosestrife has taken root along the 10-acre dune barrier, prompting concern among caretakers that the plant may spread and become the dominant vegetation, displacing native plants and eliminating sources of food and shelter for wildlife.

“We’re encouraged because the purple loosestrife has not spread beyond this stand,” said Nancy Sferra, the director of science and stewardship for the Nature Conservancy.

If the experiment at Morse Mountain succeeds, it could lead to widespread use of the beetles in other areas of Maine where purple loosestrife has begun to take hold. The beetle, the Galerucella species, can eliminate the need for herbicides or uprooting the plants by hand. Since being certified by the federal government in 1992, the insects have been released in 27 states.

The Nature Conservancy, which organized an expedition Thursday at Morse Mountain, said purple loosestrife is a Eurasian ornamental plant that appeared in this country in the 1800s. Since then, it has become an aggressive invader of North American wetlands, lakes and rivers.

The plant has started to grow on Merrymeeting Bay. With about a third of Maine’s rivers draining into the bay, there is a potential for loosestrife to spread.

In 1999, the Nature Conservancy received permission from the Maine Department of Agriculture to release 5,000 Galerucella beetles at Morse Mountain Preserve. The beetles, which are not indigenous to Maine, are produced in a laboratory in Michigan for the U.S. Department of Agriculture.

Scientists who visit the preserve twice a year have found no evidence that the beetles have damaged other plants.

“It’s a real worry, but I think we have to take some risks if we want to achieve success,” said Ann Gibbs, a horticulturist with the agriculture department and a member of the team that visited Morse Mountain.

Although it will take another two years before the full impact of the beetle program is known, Sferra said early results are encouraging. Loosestrife has remained inside the 10-acre plot and the beetles, which spend the winter in soil or leaf litter, have lived through three Maine winters.

Gibbs said the state has begun experimenting with beetle releases at other purple loosestrife sites, including locations in Lewiston, Bangor, Winslow and the Rachel Carson Wildlife Refuge.

“The beetle has not eradicated the plant, but it has definitely weakened it,” Gibbs said. “We have to remember it’s just another tool, it’s not going to end the problem.”