A galerucella beetle feeds on loosestrife leaves. (Photo by Eric Coombs, Oregon Department of Agriculture, Bugwood.org)

The Conservation Commission has approved a plan to fight an invasive species of plant in Harvard with its Europe-derived natural predators.

Kathryn Nelson of the Nashua River Watershed Association (NWRA) asked the Conservation Commission to approve a plan to release a batch of galerucella beetles in a Harvard wetland area next spring. She said the beetles feed on the leaves of purple loosestrife, an invasive plant that thrives in wetlands and chokes out a variety of native plants, reducing the habitat for waterfowl and other wildlife.

Galerucella beetle programs in the U.S. began in the early 1990s and have spread across the country, including throughout New England. Oxbow National Wildlife Refuge and Bolton Flats National Wildlife Refuge both have active loosestrife management programs. According to a Federal Fish and Wildlife report, it takes the beetles between three and five years to establish populations large enough to make a significant impact. Great Meadows National Wildlife Refuge, once a sea of purple in July and August, has returned to the greens of cattails and sedges.

Nelson cited a long-term study from Cornell University, which found that the beetles reproduced only on loosestrife and did not damage other plant species. The beetles are imported from Europe, where both they and the loosestrife originate.

For the last two years, Nelson has trained volunteers to raise the beetles over the winter for release in the late spring. Potted loosestrife plants in plastic wading pools, often kept in home basements or school classrooms, host the beetles. Females may lay as many as 300 eggs from which hatch larvae that feed on the net-covered plants until they pupate and are released to a wetland.

According to Nelson and Conservation Commission member Wendy Sisson, purple loosestrife has taken hold in the wetlands along Still River Road, in the outflow area from Bare Hill Pond.

While the beetles will not eliminate the loosestrife, they can help to keep it in check, Nelson said.

The commission approved the NWRA request unanimously.

Note: Sydney Blackwell contributed to this article.