The Department of Environmental Protection's (DEP’s) Division of Fish, Game and Wildlife recently released purple loosestrife feeding beetles on five Wildlife Management Areas (WMAs) in the northwestern part of the state. The beetles, released on the Amwell Lake (Hunterdon County), Columbia Lake (Warren County), Hainesville (Sussex County), Whittingham (Sussex County) and Paulinskill (Sussex County) WMAs will help curb a rapidly expanding population of purple loosestrife plants that are threatening New Jersey’s wetlands.
Traditional weed control relies primarily on the use of herbicides. Herbicides generally work on small, young stands of loosestrife, but have not worked well on older, more established colonies. In addition, herbicides also kill native, desirable wetland plants, are harmful to the environment and require continual application if long-term control is desired. Utilizing natural predators like the loosestrife-eating beetles is an environmentally sound, pesticide-free alternative.
Five insects, including two leaf-eating beetles, two flower-eating beetles and one root mining weevil were approved for release by the USDA Animal and Plant Health Inspection Service for introduction into the United States in 1991. Since that time, leaf-eating beetles and root mining weevils were successfully introduced onto New Jersey’s Great Swamp National Wildlife Refuge in Morris County and the Wallkill National Wildlife Refuge in Sussex County.
"Our goal is not to eradicate purple loosestrife, but rather to reduce the population to the point that it no longer dominates wetlands, so that these areas become more diverse and attractive to wetland wildlife," said division Director Bob McDowell. "Introduction of these insects is expected to be a long-term means for helping to control purple loosestrife in many areas of the country and we are pleased to work with the New Jersey Department of Agriculture in introducing the program to our wildlife management areas.”
Purple loosestrife is a perennial plant that was introduced into North America from Europe in the early 1800s. Since then, it has invaded marshes and wetlands throughout much of the United States and Canada destroying native vegetation.
Invasion by purple loosestrife results in a loss of plant species diversity and the elimination of natural foods and cover essential to many species of wetland wildlife. In fact, wetland managers in some areas of the United States feel that loosestrife has degraded more wetland habitat than human development in recent years. In New Jersey, thousands of acres of wetlands have become infested with purple loosestrife.
"Cattails, sedges, bulrushes and reed canary grass are several of the wetland plant species affected by purple loosestrife in New Jersey," McDowell said. "Waterfowl are dependent upon these plants for food and cover. Since these birds do not feed on purple loosestrife seeds and the plants have a tendency to form dense stands, such invaded wetlands are seldom used by waterfowl and their young. Furbearing mammals, particularly muskrats, seldom use these areas either, since they prefer cattails for food and shelter."
According to the Division’s Endangered and Nongame Species Program Chief Larry Niles, endangered bog turtles are especially impacted by the rapid spread of purple loosestrife, as well as several rare and endangered invertebrates including some species of dragonflies.
Purple loosestrife is also affecting several rare and endangered plant species throughout the Garden State. The DEP's Division of Parks and Forestry’s Natural Heritage Program has been studying the invasion of purple loosestrife into areas of the Delaware Water Gap National Recreation Area (DWGNRA). According to Natural Heritage Program Supervisor Tom Breden, purple loosestrife is particularly invasive of limestone bedrock areas along the banks and islands of the Delaware River within the DWGNRA where it is impacting several rare and endangered plant species.
An extremely deep root system, combined with tremendous annual seed production and rapid growth, enables loosestrife to thrive in most wetland habitats. As is common with many species of exotic or non-native plants, loosestrife flourishes in the absence of its natural insect predators. Unfortunately, native North American insects have not been able to control purple loosestrife. However, in its native habitat of Europe, loosestrife does not dominate wetland areas, since there are more than 120 species of insects present to feed on it there.