Two Highly Invasive Plant Species Targeted
(June 29, 2012) – They are not stink bugs, but they are creating quite a stir in wetlands throughout the State. The Maryland State Highway Administration (SHA) is unleashing a weevil and beetle attack on invasive plant species that choke the life out of native plants along highways and in wetlands.
SHA, along with the Maryland Department of Agriculture (MDA), is enlisting the help of the mile-a-minute weevil and the purple loosestrife beetle in the epic struggle to control invasive plant species that pose a threat to wetlands, native vegetation and wildlife habitat. Similar programs, which have been successful in New York, Delaware and other states, are using greener methods to control invasive plant species. In Maryland, SHA and MDA have used insects for the biological control of thistle, another invasive weed species.
“Weeds in gardens are a nuisance; weeds like the purple loosestrife in wetlands are destructive and can impact water quality,” said SHA Administrator Melinda B. Peters. “SHA is using safe, innovative and greener methods to control invasive species, reducing reliance on herbicides.”
SHA recently released the insects at 11 wetland sites on the lower Eastern Shore, in Central Maryland and Montgomery and Prince George’s counties. Wetlands, particularly those connected to storm water treatment systems, are critical at enhancing water quality that enters the Chesapeake Bay Watershed. Invasive plants such as purple loosestrife and mile-a-minute weed kill off plants species that support water filtration, decreasing the wetland effectiveness or even destroying it.
“The mile-a-minute weevil is doing a great job in controlling this invasive weed. The beneficial insects are plant specific and are establishing strong populations in the areas they have been released and should be effective at controlling these prolific weeds for years to come,” said Dick Bean, program manager for MDA’s Plant Protection and Weed Management Section. “Together with our state, federal and academic partners we are finding innovative ways to protect the environment for future generations and help keep Maryland smart, green and growing.”
Mile-a-minute weed is a rapidly growing vine with triangular leaves and thorns of Asian origin. It grows on shrubs, trees and other native plants species blocking necessary sunlight, ultimately killing the host plants. Because the weed is widely propagated, it is often difficult to control. The mile-a-minute vine is an annual and dies out in fall and winter, but its seeds last up to seven years and are spread by wildlife such as deer and birds.
Although purple loosestrife is alive with vibrant colors and thought to have medicinal value, its thick stands in wetlands crowd native plants, limiting biodiversity. The European perennial can alter naturally occurring water flow in a wetland, which can change the wetland hydrology. A mature purple loosestrife plant can produce up to two million seeds a year making it highly prolific.
The Mile-a-Minute Weevil
The mile-a-minute weevil is a tiny insect, about two millimeters in length that is beneficial in control of mile-a-minute weed. The tiny insects don’t harm native vegetation and feed on the leaves and stems of the mile-a-minute vine, killing it over time.
The Purple Loosestrife Beetle
The purple loosestrife beetle is a tiny insect that feeds on purple loosestrife. Adults feed on leaves, creating holes in the leaf structure. Larvae feed on developing leaf buds in early spring. Although the beetles help contain the spread of purple loosestrife, it takes approximately five years of feeding by the beetles to sufficiently control purple loosestrife in wetlands.
SHA will monitor the targeted wetland sites to document effectives of the weevils and beetles. This is not the first natural way to control unwanted plant species enlisted by the agency. SHA is continuing to use goats and sheep to manage vegetation in Hampstead that is home to the federally threatened bog turtle.