Invasive Species

Biological Control of Purple Loosestrife

Purple Loosestrife
leaf-feeding beetles,
Galerucella pusilla
and G. calmariensis

In 1997, the NH Department of Transportation’s (NHDOT) Bureau of Environment and the NH Department of Agriculture, Markets & Food (NHDAMF), Division of Plant Industry, worked together to establish a cooperative effort for the management of purple loosestrife (Lythrum salicaria) populations in New Hampshire. The project was developed in accordance with the US Department of Agriculture’s Animal Plants Health Inspection Service (USDA-APHIS) Multi-State Purple Loosestrife Project. A pilot study grant, in the amount of $30,000, was awarded by the NHDOT’s State Planning and Research (SPR) program to develop the project. Sites were selected, transects were established, and biological control agents were acquired.

As of 2004, this project has resulted in approximately 217,000 beetles being purchased for release into purple loosestrife invaded wetlands throughout the State. With the help of the community project and those sites managed by the NHDOT, all ten counties in the state are being managed with Galerucella beetles to some degree. The majority of the releases have occurred in towns in the central and southeastern portions of the state, mainly as a result of the high density of purple loosestrife occurring in these areas.

Japanese Knotweed Control

Injection of herbicide
into knotweed stems

NHDOT Control Trials Japanese knotweed (Polygonum cuspidatum), an invasive plant that is extremely difficult to eradicate, is prolific along roadways and can create not only environmental concerns but also safety and maintenance concerns. In an effort to find effective eradication methods that could eventually be utilized by NHDOT maintenance forces, three control strategies are being compared using different methods of herbicide application (cut and fill, cut and wipe, and stem injection). Control trials were started in August 2006 on NH Route 115 in Jefferson, and will continue at least through 2008. This project was initiated by the Jefferson Conservation Commission and the NHDOT Bureau of Environment, and also involves the NHDOT Roadside Development Section, Friends of Pondicherry Wildlife Refuge, US Fish & Wildlife Service, and NHDOT District 1.

A patch of Japanese
knotweed on NH
Route 115 in
Jefferson, NH.

The same patch of
knotweed in Jefferson
after a cut stem
herbicide application.

NETC Research Project

In April 2007, the New England Transportation Consortium (NETC) selected three research projects to fund, starting in fiscal year 2008. The NHDOT Bureau of Environment submitted one of the problem statements that was selected for funding: Best Management Practices for the Invasive Polygonum cuspidatum (Japanese knotweed). This project will begin during the summer of 2008, after selection of the Principle Investigator from interested New England Universities. A final report is expected approximately three years from the start of the research.

Cooperative Weed Management Areas

A Cooperative Weed Management Area (CWMA) is a partnership of federal, state, and local government agencies; individuals; and various interested groups that pool resources, set priorities, and manage invasive plants in a defined area. CWMAs are more prevalent in the western United States, but are becoming more common in the east. New Hampshire has one CWMA to date: the NH Coastal Watershed Invasive Plant Partnership. The NHDOT is a signatory to this partnership.

Best Management Practices

To address mounting concerns over invasive plants and the role NHDOT activities play in the spread of these plants along roadsides, Best Management Practices (BMPs) have been developed with input from four Maintenance Districts, the Roadside Development Section, the Bureau of Construction, and the NH Department of Agriculture.

Implementation of these BMPs will help limit the spread of invasive plants caused by maintenance and construction activities, keeping the Department in compliance with a number of State and Federal laws and regulations. NHDOT’s goal is not to eradicate all invasive plants from roadsides, but to prevent Departmental activities from spreading invasive plants to new sites.

Additional Information:

• Best Management Practices for Roadside Invasive Plants
• Invasive Plant Fact Sheet #1 - Best Management Practices for MOWING
• Invasive Plant Fact Sheet #2 - Best Management Practices for KNOTWEED

Contacts:

• Marc Laurin - Senior Environmental Manager
• Christine Perron - Senior Environmental Manager