From: Pennsylvania IPM Program
Published September 20, 2004 01:27 PM

Biological Control Successful Against Invasive Plant

UNIVERSITY PARK — A large, beautiful purple flower is disappearing from the state's streambeds and marshlands at an increasing rate, and that's a good thing. The plant is purple loosestrife, an exotic but invasive weed that is on Pennsylvania's Noxious Weed List.

The Plant Protection and Quarantine (PPQ) arm of the Animal and Plant Health Inspection Service (APHIS) of the USDA has been working in conjunction with the Pennsylvania Department of Agriculture to control it's spread. For over ten years, they have been releasing natural enemies of purple loosestrife at various sites in every county across the state. This type of biological control is part of an integrated pest management, or IPM, plan.

IPM aims to control pests — such as insects, diseases, weeds and animals — by combining physical, biological and chemical tactics that are safe and environmentally compatible.

According to Gary Clement, state plant health director for APHIS, PPQ, purple loosestrife can crowd out other marshland species, reducing the diversity of both plants and wildlife. "Without its natural predators, this exotic plant can quickly invade wetlands and dominate the native flora, as it has done in many areas of Pennsylvania," he says. Since wild and ornamental species of purple loosestrife are on the noxious weed list, their sale is prohibited statewide.

The natural enemies of purple loosestrife, all of them beetles, are beginning to make an impact. "We've been keeping track of our beetle release sites through a defoliation chart. Some sites have been hit so hard, there are no blooms in site," says Clement. He estimates that there has been an average defoliation rate of 15 to 20 percent in most release areas after an increase in beetle populations over several years.

Since there are no natural enemies of purple loosestrife native to Pennsylvania, PPQ must bring them in. According to Clement, there are only three biological control agents available to control purple loosestrife, and each specializes only on loosestrife and upon certain parts of the plant. The most successful of these are the Galerucella beetles, a leaf-eating beetle. Also being released are Hylobius, a root eating weevil, and Nanophyes, a seed-feeding weevil. "We hope to continue releasing the beetles and spread the program to more parts of the state," Clement says.

According to Clement, early detection of this invasive plant is vital. If anyone suspects they have purple loosestrife growing on their property or see it growing in streambeds or marshlands, they should contact their county's Penn State Cooperative Extension office.

For more information on purple loosestrife and other invasive weeds, please see PPQ's Web site at, or contact Clement at (717) 241-0705 or email at

The Pennsylvania IPM program, collaboration between the Pennsylvania State University and the Pennsylvania Department of Agriculture, is a partner with USDA/APHIS to communicate with the general public about the occurrence and impact of invasive species. PAIPM promotes integrated pest management in both agricultural and nonagricultural situations. For more information, contact the program at (814) 865-2839, or Web site To view our archived news releases, see Web site


For more information contact:

Kristie Auman-Bauer
Public Relations and Outreach Coordinator
PA IPM Program
(814) 865-2839

Terms of Use | Privacy Policy

2018©. Copyright Environmental News Network