Contact Information:
Debra Eberts
Bureau of Reclamation
P.O. Box 25007, Mailcode 86-68220
Denver, CO 80225
phone: (303) 445-2217
E-mail: deberts@do.usbr.gov
The Researcher
I have been a botanist in the Environmental Research and Investigations Group (86-68220) of the Bureau of Reclamation (Reclamation) since 1991. The 6-member team I work in helps Reclamation regional and area offices manage weed and pest species problems using Integrated Pest Management (IPM) techniques. These techniques combine the use of chemical, mechanical, cultural, and biological controls. Each of us in the team has areas of specialization, and one of mine is research on the biological control of weeds using insects. I have a number of projects in progress producing and using insects to control leafy spurge, yellow starthistle, saltcedar, spotted knapweed, and purple loosestrife. I am also involved in developing methods to map distribution of weeds and to revegetate areas affected by weed control.
In 1995, I began a project using insects to control purple loosestrife on Reclamation facilities in central Washington state. This project has developed into an excellent demonstration of the potential of biological controls: 
Purple loosestrife (Lythrum salicaria) plants are found in habitats where cattails grow. The plants range in height from 2 to 8 feet, depending on growing conditions, and the showy purple flower spikes (which bloom from late June to late August) can reach lengths of 3 feet. Other identifying features of the plant are its oppositely-paired leaves and square stems.
The Weed
Purple loosestrife (Lythrum salicaria) is a perennial, non-native plant with attractive purple flower spikes. It crowds out desirable wetland plants because it grows tall, grows fast and reproduces in large numbers (just one plant can produce several million seeds a year). When loosestrife was introduced to this country from Europe, the insects that keep it in check in its homeland did not come along. This gives it another growth advantage over native plants - while they are being munched on by insects and animals, the unpalatable loosestrife just keeps growing.
The resulting dense stands of woody loosestrife stems are nearly impossible for people and wildlife to travel through. And, since the plants can grow out into water about 18 inches deep, these stems catch soil and debris and cause rapid filling-in of waterways. Not only does loosestrife affect the movement of water through Reclamation waterways, it also degrades associated wetlands by replacing food and habitat plants required by wildlife with a plant that is of little value to many species.
The Setting
The Winchester Wasteway, part of the Columbia Basin Project, is in central Washington near Moses Lake. It collects return flows from farm irrigation in the upper third of the project for reuse in the southern portion to irrigate another 250,000 acres. This wasteway is over 30 miles long, and since 1963 had become infested with over 20,000 acres of dense purple loosestrife. The thick stands of woody loosestrife threatened to block the flow of water. This region receives less than 10 inches of rain a year, so delivery of irrigation water to farmers is critical. Herbicidal control of plants was done on a limited basis, but the monetary and environmental costs to repeatedly spray such a large area are prohibitive.
Closeups of Galerucella adult and larva. Both stages feed on leaves of purple loosestrife. Actual size of the adult beetle is 3-5 mm.
The purple loosestrife plant in the foreground has been eaten by larvae and adults. Note the flowering plants in the background.
Biological control of weeds involves the planned use of a predator or disease-producing organism to reduce the vigor, reproduction, or density of the target weed. When purple loosestrife was introduced to this country from Europe, the insects that naturally limit its growth in its homeland did not come along. To restore balance, we have now introduced several species of these insects to the United States. The ones giving the striking results at the Winchester Wasteway are two beetles, Galerucella calmariensis and Galerucella pusilla. Before the beetles were allowed into this country from Europe, they were tested to see if they would cause any problems. Experiments were done to see if they were "host specific", or if they’d eat any other plants besides purple loosestrife; we didn’t want to bring over another insect that would eat other wetland plants or important crops. They also got a health checkup so they didn’t bring in any diseases that could harm our native insects.
Both the adults and larvae of Galerucella calmariensis and Galerucella pusilla feed on the leaves of purple loosestrife. (The two species are difficult to tell apart, and will be discussed as a combined group.) The adult beetles spend the winter in the soil and plant litter. They emerge in the spring after the loosestrife plants have begun to grow and lay eggs on the leaves and stems. The developing larvae feed on leaves and growing points of the plant, limiting the plants’ growth and flowering. The larvae pupate in the soil before emerging as adults the same year in early summer. The number of generations per season varies from one in cooler areas to two or possibly more in hotter areas with longer growing seasons. Adults generally live for a year or less.
I received a colony of Galerucella spp from Dr. Bernd Blossey (Director, Biological Control of Non-Indigenous Plant Species Program, Cornell University) in 1994, and began mass-production of the insects at the Denver Federal Center. Each year from 1995 through 1998, insects were produced and shipped to Reclamation’s Ephrata, WA office and released at the Winchester Wasteway by Mr. Craig Conley (Reclamation, Conservation Agronomist, Ephrata, WA). The total number of Galerucella spp adults released from Bureau of Reclamation mass-production programs was about 40,000. During this time, we monitored the number of insects at the site and made measurements of plant vigor, including height, density and flowering. We also took aerial photos of nearly 6,000 acres of the Winchester Wasteway area in 1995 and again in 1998.
The photographs of the Winchester Wasteway show dramatic changes in the vegetation between 1995 and 1998. How can we prove that these dramatic changes are due to the effects of the biocontrol insects and not some environmental problem like drought or global warming? Visual observations of plants devoured by adults and larvae would seem to be convincing, but we also collected data on the weather and insect and plant parameters. The graph shows a small part of the data collected and illustrates that as the numbers of insects increased, the height and density of purple loosestrife decreased.
Using biological control insects doesn’t necessarily mean that all the purple loosestrife will be eliminated forever. Instead, a balance between the numbers of insects and plants should eventually be reached. A little loosestrife is not a bad thing; only when it "takes over" does it cause problems - restricting water flows and reducing wildlife habitat.
The next step in the recovery process at the Winchester Wasteway will be to revegetate the areas where the purple loosestrife has been removed. Experiments are in progress to determine the best methods to establish desirable plants over such a large disturbed area. We will be testing such methods as burning away the woody canes so the area is more accessible and less shaded. It is important to revegetate this area as quickly as possible before another weed moves in to fill the space once occupied by purple loosestrife.