Kitsy Snow and other members of the Ridgefield Conservation Commission released 1,500 weevils Thursday morning at an open space parcel on Laurel Hill Road. The insect is bred to destroy the invasive plant known as mile-a-minute vine.
A small, herbivorous insect is the town’s only biological solution to controlling mile-a-minute vine, the fast-growing and rapidly spreading invasive plant now found in most Fairfield County towns.
Plant scientists at the University of Connecticut and members of the Ridgefield Conservation Commission released 1,500 “mile-a-minute weevils,” scientifically known as Rhinocomimus latipes Thursday at an open space parcel on Laurel Hill Road to combat the dangerous plant.
“We’re never going to truly get rid of mile-a-minute vine but we can control its growth,” said Donna Ellis, a teacher at UConn’s Department of Plant Science and Landscape Architecture. “The goal is to allow the growth of new plants and improve the quality of life in these affected habitats.”
Dr. Ellis, who is also the co-chairman of the Connecticut Invasive Plant Working Group, found a few hundred weevils already going to work at the site before the release.
“She was pleased and a bit surprised that some weevils have already migrated here from other towns,” said Benjamin Oko, a member of the Conservation Commission. “They’re not nearly enough to control the plant, though, so she decided to release the 1,500 she brought with her.”
A large stand of mile-a-minute vines on Laurel Hill Road.
Dr. Oko described the weevils as small creatures that look like a “tick in its larva stage.”
The weevils are raised in quarantined labs in New Jersey and bred to specifically attack and feed off mile-a-minute vine. They are tested several times before being released in the wild.
These “weevils don’t eat or attack any other plants or animals,” Dr. Ellis said. “Their appetite is limited to only eating the mile-a-minute vine — they need the plant to sustain themselves and reproduce.”
Mile-a-minute vine comes from Asia and matures during the summer when it “smothers other vegetation” through blocking out sunlight for plant seeds that are underneath or around it.
It can grow up to 25 feet a year and up to six inches a day.
The vine dies in late autumn when the ground begins to frost. However, the plant’s seeds remain in the ground.
“The seed carries the plant each year and the vine always comes back out of the ground in the spring — seeds can live up to seven years in the right soil,” Dr. Ellis said. “The plant outcompetes other native plant species and kills them off rapidly.”
The mile-a-minute weevil, scientifically known as the Rhinocomimus latipes, eats away at the mile-a-minute vine that was found in Ridgefield last summer at an open space parcel on Laurel Hill Road. —Donna Ellis, UConn
One of the major problems to the biological solution is the number of weevils available is limited. In addition, once released, the weevils’ reproduction cycle is slow.
“A town using these weevils depends a lot on availability — they’re always limited and not available in large quantities,” Dr. Ellis said. “Most locations have seen an increase in feeding damage, but it’s over a longer period of time. It takes years to build up the weevil population in an area.”
Despite these setbacks, UConn continues to get allocated funds each year from the United States Department of Agriculture.
“Biological controls have gotten mixed reviews over the years when applied to different scientific strategies,” Dr. Oko said. “We hope this doesn’t get mixed reviews. Although we won’t ever be able to eliminate the plant using these insects, it’s worth a try to limit its spreading in the area.”
Dr. Ellis was pleased with the discovery of weevils existing in Ridgefield before Thursday’s release because she believes it justifies that the program is working in Fairfield County.
“We always recommend to hand pull the vine at first sight in the spring,” she said. “We then recommend a biological approach using the weevils, if they’re available, because they move from location to location and are great at dispersing to different affected areas and limiting the vine’s growth.
“We don’t have enough resources that every person and property with the vine has access to the weevils.”
The first town to release weevils was North Haven in 2009.
The invasive plant was first discovered in Ridgefield last summer, but the insects were not available to release until last week.
Ridgefield was the 16th town in Connecticut that elected to implement the biological-based solution.
Now, there are more than 32,500 weevils that have been released in 17 towns. The number of weevils per site ranges from 500 to 2,000.
The conservation commission voted to approve the weevils around three weeks ago, according to Dr. Oko.
“It’s expensive to control mile-a-minute but the commission is unanimously in favor of releasing these insects because we believe they will help limit the plant’s growth here in town,” he said.
He added that the commission believes the plant is at more than one location in town.
Adult weevils feed on the exterior of the plant’s leaves, while the premature, developing insects attack the plant on the interior.
Dr. Ellis, who also works with the Department of Energy and Environmental Protection (DEEP) and the Connecticut Agricultural Experiment Station (CAES), said that members of the conservation commission can stop by the open space area on Laurel Hill to gauge the growth of the weevil community.
“I’m sure they have other projects they are working on but they can go out and study the insects’ impact at any time if they want,” she said.
Dr. Ellis will return to Ridgefield — for one of her three annual field surveys — with her students in September to evaluate the land around the invasive plant.
In their assessments, the scientists count feed damage, the number of plant seeds in the soil and the number of weevils in the area.
“We go out three times a year to measure the population, to monitor any changes that have happened and to track where the plant is,” she explained. “We always hope to see the plant decreasing.”