Project Overview

Michigan State University is working with K-12 teaching professionals, naturalists, property managers and citizen groups to control purple loosestrife and foster stewardship of our natural resources. We are rearing and releasing natural enemies of the invasive weed and encouraging others to do the same. The project is being funded by Michigan State University, Michigan Sea Grant, Michigan Department of Agriculture, Michigan Department of Natural Resources, Michigan Department of Environmental Quality, and the US Environmental Protection Agency.

Message from the PLP Coordinators
The Purple Loosestrife Project at Michigan State University was initiated in January 1997 to couple biological control of purple loosestrife with an innovative outreach and education program. The project aims to restore the biological diversity, integrity and ecological function of wetlands degraded by purple loosestrife and offer a unique opportunity to enhance science and environmental education for Michigan youth by actively engaging local communities in both processes. We hope you will join us!

Goal Statement
We intend to reduce purple loosestrife density using the plant's own natural enemies, thereby improving circumstances for native species to reestablish themselves. We will engage Michigan citizens and encourage local land stewardship to accomplish this goal.

Project Background
The Problem: Purple loosestrife (Lythrum salicaria) is a European plant species which is an aggressive invader of North American wetlands, lakes and rivers.  Once established, purple loosestrife can become the dominant vegetation, forming monospecific stands which significantly reduce biodiversity and degrade habitat quality.  Of primary concern is that purple loosestrife displaces native plants eliminating food and shelter for wildlife and other species.  While strikingly colorful in flower, dense stands of loosestrife also impair recreational use of wetlands and rivers, impede water flow in drainage ditches and invade rightofways, requiring costly management efforts.  Purple loosestrife is a widespread and serious problem, affecting both coastal and inland wetlands, lakes and waterways throughout the Great Lakes region.  In Michigan, purple loosestrife is present throughout the lower peninsula and is expanding its range in the upper peninsula.  To date, few viable solutions for managing this invasive weed have emerged.  Control by conventional means (water level management, burning, herbicides, direct digging, cutting) has proven to be extremely difficult and is impractical on a large scale.  An alternative is the biological control of purple loosestrife by introduction of natural enemies from its native range.

Three species of plant feeding beetles, Galerucella calmariensis, G. pusilla and Hylobius transversovittatus show promise as biological controls for purple loosestrife.  Native to Europe, these insects have undergone extensive testing to determine their safety and effectiveness, receiving USDA approval in 1992.  Since then, these insects have been released in 27 states and all the Canadian provinces. The Galerucella leaf beetles feed on bud, leaf and stem tissue causing defoliation and prevention of flowering/seed production.  Continued defoliation leads to plant death. Hylobius is a weevil whose larvae mine in root tissue weakening and ultimately killing the plant.  Recent results from Ontario, Minnesota, and our own Michigan release sites indicate that the Gallerucella beetles can have a dramatic impact on purple loosestrife infestations is as little as three years. 

Beginning in 1994, the Michigan Department of Natural Resources, Wildlife Division, petitioned the Michigan Department of Agriculture for approval to release these insects on several infested state game areas in Michigan. The MDNR's releases of about 5,000 Galerucella in 1994 have established and are beginning to show impacts.  The result of similar releases in 1996 of Galerucella and Hylobius are still uncertain.  While these natural enemies cannot eliminate purple loosestrife, experts believe that in combination they are capable of reducing the density of purple loosestrife by 90% over most its current range.  Reducing purple loosestrife density will allow reestablishment of native wetland vegetation.

The challenge is to establish viable populations of these natural enemies in Michigan watersheds where purple loosestrife occurs.  The rearing and release procedures are quite simple but rather labor intensive.  By training and supporting other groups interested in rearing these natural enemies it will be possible to greatly multiply the number of beetles reared and release sites impacted.

Since the inception of the project we have established dozens of viable populations of the Galerucella beetles in purple loosestrife infested watersheds in Michigan and initiated evaluation of the impacts of many of these releases. Perhaps as importantly, we have involved local stakeholder groups in a meaningful way, resulting in the formation of partnerships among various interest groups involved in wetland management, use and conservation. These partners assist in the process of educating youth and the public on the project, resulting in greater understanding of biological control and the desirability of its use. As Michigan faces continued challenges from invasive species and loss of effective conventional control tactics, a public which is knowledgeable and supportive of biological control techniques will be a great asset.