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URI Researchers using Bugs to Fight Invasive Plant in Rhode Island

The mile-a-minute vine, an invasive from the Far East that has taken root in several Rhode Island communities, has a new enemy thanks to URI researchers: hundreds of tiny weevils.

Weevils used by URI researchers to control the mile-a-minute invasive vine are released. (Photo: Michael Salerno Photography)
Weevils used by URI researchers to control the mile-a-minute invasive vine are released. (Photo: Michael Salerno Photography)
In select spots in Cranston, East Greenwich and Hopkinton, an army of tiny weevils are munching on a feast of mile-a-minute, an aggressive non-native plant with Far East origins that has been steadily encroaching native habitats in Rhode Island.

The plant, which can grow upwards of six-inches a day, is the target of a University of Rhode Island biocontrol effort designed curb its growth without affecting the region’s native species.

The weapon: 18,000 weevils that will self-perpetuate and ideally, keep the triangular-leaved vine under control.

"Mile-a-minute is a very persistent plant that is difficult to get rid of,” said Lisa Tewksbury, a URI entomologist who is rearing the weevils for release this year. “We know that biocontrol works on this plant, so we’re hoping the weevil population will be self-perpetuating and they will keep mile-a-minute under control.”

Tewksbury asks the public to report populations of mile-a-minute vine so she can release weevils in those locations later this year. She can be reached at 401-874-2750 or lisat@uri.edu. To identify the plant, visit www.mam.uconn.edu/speciesID.html

Mile-a-minute was first discovered in the United States in the 1930s in the Mid-Atlantic States, where it is believed to have arrived via the horticulture trade. Since then it has spread to 10 states and become established along roadsides and streams, moving from place to place in the water and via animals that eat and distribute it. 

Research on a biological control of the plant began in Delaware and New Jersey in 1996, and the weevil was approved for release in 2004. The feeding by adult weevils creates holes in the leaves of the plant, and females lay their eggs in the leaf tips. After hatching, the larvae feed inside the stem, preventing the plant from flowering and producing seeds. 

Tewksbury released the first batch of weevils in Rhode Island in 2009 at a site in Cranston, with additional releases every year since 2011 in Cranston and East Greenwich. Weevils were first released in Hopkinton in 2013. Populations of mile-a-minute have also been found on Block Island, but Tewksbury has not released the insects there yet.

When the lab in New Jersey that was rearing the insects reached its capacity, Tewksbury began raising the insects at the URI BioControl Lab, with funding from the U.S. Forest Service and the U.S. Department of Agriculture. Some of the weevils reared at URI are shared with researchers in Massachusetts and Connecticut.

Tewksbury hopes that the weevils will do their job without requiring further releases in subsequent years, though she plans to continue to monitor mile-a-minute and the weevils for some time. She is now studying other invasive plants that can be controlled by insects, including a caterpillar that feeds on swallow-wort and a weevil that eats knapweed.

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