Asian Insects Battle With Invasive Vine

By Kendra Bobowick

Since the summer of 2009 a small insect from China has been thriving on — and hopefully will one day control — the invasive mile-a-minute vine found in Newtown, among other Connecticut towns.

“The feeding damage” done in the last two years by the minute insect as it sustains itself on the invasive vine in Newtown “is significant,” said Donna Ellis, the senior extension educator at the University of Connecticut’s Department of Plant Science and Landscape Architecture.

Of the three initial release sites in town to which a fourth has been added, where several hundred to more than a thousand weevils quickly sought the underside of leaves as researchers shook them onto the plants, the Middleton Road site shows the most activity. “This site is particularly interesting,” Ms Ellis said, compared to two locations along Huntingtown Road and another off Deep Brook Road. The Middleton site near Mt Pleasant Road — unlike the Huntingtown Road locations along the Pootatuck River Banks — was not flooded by early spring rain or beaver dams.

A recent inspection at the Middleton area found weevils “right at the shoot tips,” she said, and the weevil counts were also good.

Overall, all sites “have weevil activity,” she said. “The weevils are established.” The weevils reproduce every 25–30 days, and Ms Ellis expects two to four generations to take place in one summer.

Also involved in the Newtown sites since 2009 is Todd L. Mervosh, PhD, weed scientist and diagnostician with the Connecticut Agricultural Experiment Station. He noted recently, “You’ve seen how tiny they are. It takes so many to make a dent.” He and others are “counting on them” to build their populations, he said.

Land Use Deputy Director Rob Sibley cannot say for sure what the weevil outcome will be “until the study plays out,” but to date, he notes an “excellent response in the spread of weevils on mile-a-minute.”

“The idea is to keep the plants from reproducing, and then we’ve won the battle,” he said. Mr Sibley does not know of anything in Newtown that will eat the weevil, and they have survived two winters. “We’re excited about how we’re doing.”

The vine is not heavy and woody, but it has an “amazing growth rate and there is so much of it,” Ms Ellis said this week. The vine will continue to grow through to the first frost. Wildlife will disperse the seeds, which can also float in streams. To combat the native Eastern Asian species, science “went back to the country of origin to see what attacks it natively.”

The weevil, which feeds primarily on the mile-a-minute (MAM) vine, is a good biological combatant, she said. Ms Ellis feels the Newtown locations are “in good shape.” Although the weevils have survived winters here and appear to be surviving, she looked ahead. “It’s hard to say when we’ll see total control; I feel it will be a number of years, maybe five or more, but we’ll see it.”

Thinking about Ms Ellis’s five-year possibility, Dr Mervosh said, “It could be…” Mentioning the Middleton site, he said, “The level of control was much more than other sites. The MAM was riddled with weevils.” Long-term, he does not believe that either the weevil or the vine population will completely die.

“The way bio-control works is the agent — the weevil — never completely eradicates the host plant,” he said. The near, but not complete eradication will also reduce risks that weevils might start feeding on another species, he said. So far they have found no evidence at the site that weevils have survived on plants other than MAM.

 

Background

The mile-a-minute vine (Polygonum Perfoliatum) was first spotted in Newtown during the summer of 2007. Sightings had volunteers and officials tearing it out yard by yard, and by 2009, the state’s Department of Agriculture, the then Department of Environmental Protection, now the Department of Environmental and Energy Protection, and the University of Connecticut Extension Center received approval from the Federal Department of Agriculture to release the weevils in Connecticut, including several Newtown sites. The Newtown Land Use Agency is also collaborating on the project.

At that time, Ms Ellis had explained that the adult weevils chew holes in leaves and lay eggs and immature weevils eat into the plant stems. She also offered sound predictions. She had said, the process would take time for the weevils to become established. “The idea? They’ll build up a population; they’ll slowly build up numbers.” And, they have.