Beetle-mania: Researcher releases thousands of beetles to control invasive plant
Todd McLeish, 401-874-7892
KINGSTON, R.I. -- August 16, 2005 -- Purple loosestrife is an attractive flowering plant introduced into the U.S. from Europe and Asia, but it crowds out native plants, takes over wetlands, and with no natural enemies, it spreads quickly. Land managers’ efforts to yank it out, mow it down and burn it has done little to control its growth.
So a University of Rhode Island researcher is using the plant’s number one enemy, Galerucella beetles, which are native to the plant’s homeland, to eradicate it in select Rhode Island locations.
At the request of the R.I. Department of Transportation, URI’s Lisa Tewksbury provided 7,000 of the small brown beetles for release in July along Routes 4, 95 and 295 where loosestrife has caused drainage problems in roadside ditches. Tewksbury provided an additional 2,500 beetles for release adjacent to the Pawcatuck River on Route 112 in Carolina last month in a partnership with the Wood-Pawcatuck Watershed Association.
“About 100 insects have been identified that feed on purple loosestrife in Europe, but the Galerucella beetles is one of the few that feed on loosestrife and almost nothing else. A lot of research has gone into ‘host specificity trials’ to make sure that the beetle won’t harm other plants,” said Tewksbury. “This is a national project, and the same beetle has been released in many states.”
Tewksbury first experimented with Galerucella beetles in 1996 when the large wetland at Roger Williams Park Zoo in Providence was overrun with purple loosestrife. Within two years, the beetles, which eat the plant’s leaves and stems, defoliated a patch of the invasive plant, and they have kept the plant in check ever since.
When Tewksbury was first contacted by DOT in 2003, she was happy to put another batch of beetles to work. After releasing a small number of beetles that year, she reared thousands of additional beetles in an outdoor cage for release in 2004, and she increased the effort this year. DOT contributed $1,000 to support the rearing project.
The Pawcatuck River site was one that the URI scientist passed on her way to work every day, and she contacted the watershed association in 2004 and offered to provide the beetles before the plants got out of hand. The association has contributed $500 to the effort and is working with a URI student intern and a team of volunteers to monitor the project.
“The beetles are the most effective long-term control method,” said Tewksbury, “because anything else you try – like pesticides or hand pulling it out – has to be done over and over again every year.”
She said it will likely take two or three years for the beetles’ impact on the loosestrife to be noticeable.