Beetle Farmers:  A Solution for Purple Loosestrife

Donna R. Ellis, Senior Extension Educator
University of Connecticut
Department of Plant Science and Landscape Architecture
August 28, 2009

Invasive non-native plants such as purple loosestrife (Lythrum salicaria) are a serious concern because they grow and establish quickly over wide areas and decrease the abundance of native species, reducing biological diversity in wetlands, meadows, forests, and other natural areas.  Invasive plants may produce high numbers of seeds and/or have extensive creeping underground rhizomes to invade and spread rapidly.  Integrated Pest Management (IPM) methods can be used to control invasive plants in natural and managed landscapes.  IPM technologies include the use of biological, mechanical, cultural, and chemical controls.  Biological control, the use of natural enemies to reduce an invasive plant's population below a biological or economic threshold, is a sustainable, low-input method to control purple loosestrife.

Purple Loosestrife in bloom
Galerucella beetle adult

Galerucella leaf-feeding beetles are approved for biological control of purple loosestrife.  These beneficial insects have been introduced into Connecticut wetlands since 1996.  The beetles feed primarily on purple loosestrife and do not prefer other kinds of plants.  Feeding injury by the beetles helps to reduce purple loosestrife populations that invade wetland habitats in Connecticut and throughout the United States.  A diverse group of more than 725 Connecticut citizens has received training to participate in the statewide purple loosestrife Beetle Farmer Program.  The results continue to be excellent, with the introduction of more than 1.7 million Galerucella beetles into wetlands where purple loosestrife control is needed.  Beetle Farmers and purple loosestrife biological control are topics that have been included in IPM and environmental science curricula for K-12 students developed by University of Connecticut scientists and area teachers.  The UConn IPM website, including information on Beetle Farming, can be found on the web at www.hort.uconn.edu/ipm.

The Beetle Farmer Program began at the University of Connecticut in the Department of Plant Science and Landscape Architecture in 2004 to enhance educational outreach for biological control and to increase the distribution of the Galerucella beetles in the state.  Raising beetles to control purple loosestrife through the Beetle Farmer Program is an exciting opportunity for community involvement by people of all ages.  If you know of a site invaded by purple loosestrife where biological control is desired, or if you would like to raise Galerucella beetles to release at a particular site, become a Beetle Farmer and start this successful program in your community.

The primary vehicles used for communicating information are the UConn Beetle Farmer website and the Beetle Farmer list serve (an electronic mailing list). The website contains photographs and descriptive information about purple loosestrife and the Galerucella beetles, a training video and a PowerPoint presentation with step-by-step instructions on Beetle Farming, a distribution map depicting towns where the beetles have been introduced, a rearing guide for the beetles, newspaper articles, program summaries, and much more.  Beetle Farmers receive timely information about the program via the list serve in an interactive format.

What are the steps involved in Beetle Farming?  Here is a timeline of Beetle Farmer activities: 

February and March

February through March is a good time to become acquainted with the statewide program, learning about the biology of both the Galerucella beetles and purple loosestrife and the problems that invasive non-native plants create in natural areas.  Visit the UConn Beetle Farmer website for training tools and other helpful information. 

You should also begin procuring supplies (see Beetle Farmer website for supply list), but the project does not require a large budget for the items needed.  For example, used three-gallon containers and potting mix can be donated by local garden centers and homeowners.  Sleeve cages made of bridal veil material or noseeum netting that are used to cover the plants while the Galerucella beetles go through their life cycle can be purchased or sewn, if you are handy with a sewing machine. 

April

You will need to dig purple loosestrife plants by the third week in April and put them in the containers so they will have time to grow before introducing the adult Galerucella beetles onto them.  If you subscribe to the Beetle Farmer list serve, you will receive announcements for “Dig Days” where you can meet other Beetle Farmers at wetlands to dig purple loosestrife plants for the project.

Space requirements for this project are minimal, depending on the final number of Galerucella beetles desired.  If you want to grow just one or two plants, you can put each plant in a plastic dishpan half-filled with water.  At the University of Connecticut, 24 potted purple loosestrife plants have been grown in two small wading pools and only need a 5-foot x 10-foot area. 

May

Once the plants have reached 18 inches in height, you will visit a field insectary to collect a ‘starter colony’ of beetles to put on the caged plants.  Field insectaries are wetlands where the Galerucella beetles have already been introduced, have become established, and are controlling purple loosestrife.  You will receive announcements on the Beetle Farmer list serve for “Beetle Collection Days” beginning in late May where you can gather the starter colony of beetles for your plants.  Approximately 15 adult Galerucella beetles are introduced onto each potted purple loosestrife plant.

If the purple loosestrife plants are healthy and an average of 15 adult beetles is introduced onto each plant, approximately 1,500 new beetles (offspring) will be produced per plant. 

June

We encourage all Beetle Farmers to release their new generation beetles in local wetlands so that the site can be visited each season to monitor the progress of the beneficial insects in controlling purple loosestrife.   Connecticut has Federal and State permits that allow the introduction of the beetles.  A consent form needs to be signed by the property owner or person responsible for each new wetland site to allow the beetles to be released. 

One suggestion to assist you in locating a release site is to contact your local Inland Wetlands or Conservation Commission to find areas where purple loosestrife is growing and where control of this invasive plant is desired.  You are welcome to contact me for a possible release site, as I have information on many field locations in Connecticut where purple loosestrife has been documented.  Land trusts and municipal properties may be suitable as local release sites.

Any type of wetland with a minimum of one-tenth to one-quarter acre of purple loosestrife can be used as a release site.  Wetland habitats may include wet meadows, marshes, and edges of ponds and lakes.  Over the years we have found that the beetles, which overwinter underground as adults, will survive in a site that undergoes some seasonal flooding in the spring, but the insects do not do well at a site with prolonged seasonal flooding. 

July

The beetles need a 4˝ to 6 week period to complete their life cycle on the sleeve-caged plants.  Once the new generation beetles begin to emerge from the soil in the containers, you will observe them crawling on the inside of the cages.  At this point, simply transport the containers of purple loosestrife to the release site and remove the sleeve cages.  The releases will likely occur in the first part of July.

Biological control is a patient process, with large wetlands requiring an average of seven years before significant reduction of purple loosestrife populations may be observed.  The results will be very rewarding, however, as you witness the gradual return of native wetland flora and the diversity of wildlife that it supports.

To sign up for the Beetle Farmer Program, contact Donna Ellis at the University of Connecticut [phone: (860) 486-6448; email: donna.ellis@uconn.edu

This article appeared in Connecticut Nursery and Landscape magazine (Issue 1, 2010; pp. 20-23)

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