FAIRFIELD, Vt. – Residents of Fairfield Pond used to pull Eurasian watermilfoil out by hand – a backbreaking job that ate up weekends. But now a tiny bug is doing the work for them, controlling an invasive plant that is clogging some lakes and ponds in Vermont.

“The weevil is a fantastic thing. It’s natural. It does the work for you,” Bruce Callopy, president of the Fairfield Pond Association, said Saturday.

Three years after Middlebury College biology professor Sallie Sheldon added 8,834 weevils to the pond’s milfoil beds in 2005 and 28,399 the next year, the weeds have thinned and the weevils are hollowing out the plants’ stems.

“Most places where there was dense Eurasian watermilfoil there are now sprigs. Some places it’s still relatively dense but there’s no flowering which means that there’s been some damage. And some beds that were Eurasian milfoil, there’s now just native plants,” she said.

That’s a big improvement over other summers.

“It would be in a 50-foot section and then the next summer that bed would be 350 feet long, you just kept seeing it grow and grow and grow,” said Sally Ann Callopy, secretary and treasurer of the Fairfield Pond group.

Milfoil is a fast growing nonnative plant with feathery foliage that can form dense beds on the surface, choking water for boaters and swimmers, fish and native plants. Fragments can spread quickly on boats from one waterway to the next and there’s no way to get rid of it once it takes hold.

Residents of Fairfield Pond have tried pulling it, mowing the lake bottom with a harvesting machine, and suctioning it. Other lake groups have used herbicides.

But the lakes that have shown the greatest decline in milfoil are the ones where weevils exist and no controls have been used, Sheldon said.

Weevils are not new to Vermont. But the Fairfield Pond project is the largest use of them so far in the state, Sheldon said.

The problem is that no one is growing weevils on a large scale, she said. An Ohio company sells them in large quantities but the state isn’t thrilled about introducing weevils from outside of Vermont, she said.

Agency of Natural Resources officials could not be reached for comment Saturday.

According to a Vermont Department of Environmental Conservation Web site last updated in 2001, weevils have been added to 10 lakes since 1993, with more than 100,000 weevil adults, eggs and larvae introduced.

The state provided $5,000 for the Fairfield Pond weevil experiment. Sheldon raised the bugs herself.