Beneficial beetles control invasive plants in the Upper Delaware

With the coming of August, an attractive carpet of purple flowers is becoming evident in many areas, especially along the shore of the Delaware River. Unfortunately, these flowers are most likely the Purple Loosetrife plant (Lythrum salicaria). This plant is an invasive species that favors wetlands such as lake shores and river banks. It chokes out native species of plants and can cause habitat loss for wildlife that depend on the native plants for food or shelter.

Fortunately, an ally has been found in the control of purple loosestrife in the form of a brown beetle about the size of a grain of rice: the galerucella beetle.

Galerucella beetles feed upon purple loosestrife, and this beetle is very host specific toward purple loosestrife. This beetle will feed on purple loosestrife and nothing else, which makes this beetle a great biological control.

According to Natural Resource Specialist Don Hamilton of the National Park Service’s Upper Delaware Scenic and Recreational River, galerucella beetles were first released in 2004 along a purple loosestrife-infested riverbank in the Pond Eddy area. Since then, annual surveys have shown promise in the form of plant damage and the reduction of plants within the expanding range of the galerucella beetle.

For additional information contact Hamilton at don_hamilton@nps.gov or call 570/729-7842.