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Bugging Purple Loosestrife

It was a hot May morning, and botanist Debra Eberts looked around as she waited for the boat to arrive at the Dodson Road boat ramp in central Washington state. She noticed that her white rental car and tick-check white clothes were covered with small brown beetles about the size of a dieting ladybug. Boating down the narrow waterway, bordered by tall wetland plants, did not provide escape from the pesky beetles, either. They continuously crash-landed and crawled around the boat. Eberts saw more floating in large buoyant groups on the water.

The Galerucella beetle feeds on purple loosestrife leaves. It was releases as a biological control in August of 1995. Photo by B. Blossey, Cornell University

It wasn't any different at her destination in the Winchester Wasteway. All the vegetation had burned that winter, and the beetles were thick on the moss-like mat of newly germinated seedlings. Bugs that couldn't fit into the seething masses at her feet flew around agitatedly before discovering she was a handy landing site.

Though this may seem like a nightmare, it was a dream-come-true for Eberts, a Bureau of Reclamation botanist. She had just arrived from Denver to check the progress of a biological control project at Reclamation's Columbia Basin Project in central Washington. The beetles she was admiring were descendants of Galerucella beetles she had released in 1995 to combat purple loosestrife, an invasive wetland weed.

The abundant leaf-eating beetles were doing the job, she found, helping to keep the irrigation water flowing in the river. "We only receive 10 inches of rain a year in this area," noted Craig Conley, a Reclamation conservation agronomist from Ephrata, Washington. "So farmers must rely on irrigation. The dense purple loosestrife was threatening to block the flow."

The 30-mile-long Winchester Wasteway is a vital part of the water's path. It collects return flows from farm irrigation in the upper third of the project so that it can be reused to irrigate another 250,000 acres. In the early 1960s, as the newly created wasteway (which courses through a desert) was receiving water and becoming a wetland, a university experiment introduced purple loosestrife to the area.

The aggressive purple loosestrife (Lythrum salicaria) had little competition from other wetland plants and quickly spread across almost 20,000 acres. A perennial, non-native plant with attractive purple flower spikes, the invasive species is a deadly plant for wetlands across the United States. It crowds out desirable wetland plants because it grows tall and fast and reproduces in large numbers-one plant can produce several million seeds a year. First introduced to the United States in the early 1800s near New York City, purple loosestrife was widely used in gardens and commonly sold in nurseries. But the insects that keep it in check in Europe did not come along with the plant. Once established-it is now found in nearly all states-this aggressive invader of wetlands can destroy marshes and choke waterways.

In the Winchester Wasteway, purple loosestrife was also ruining critical wildlife and waterfowl habitat in both the desert wildlife recreational area (through which the wasteway flows) and the nearby Potholes/Columbia National Wildlife Refuge. And the plant was a major nuisance for boaters, anglers, hunters, and others who used these areas for recreation.

Herbicidal control was attempted on a limited basis, but the monetary and environmental costs to repeatedly spray such a large area were prohibitive. Biological control of purple loosestrife using insects seemed the only hope.

The Winchester Waterway in central Washington prior to the release of the Galerucella beetles as a biological control in August 1995 Photo by F. Nibling

The same site in August 1998 shows native cattails and bulrush, which were not harmed by the beetles and will provide a seed source for revegetation. Photo by D. Eberts

"Several insects had recently been approved by the U.S. Department of Agriculture for use in control of purple loosestrife," Eberts recalled. "While we knew they would eat only purple loosestrife, we didn't know how much they would eat. And for a site this big, we had to figure out a way to raise large numbers of insects for release."

A search for help led her to Bernd Blossey at Cornell University. Blossey supplied a "starter-kit" of insects, and Eberts began experimenting with ways to mass-produce the beetles. The resulting bugs were shipped to Craig Conley, who released them at the Wasteway in 1995.

The Hylobius weevil feeds on purple loosestrife roots. It will be released to deplete the purple loosestrife food reserves. Photo by B. Blossey, Cornell University

Eberts and Conley waited eagerly, worried about how long it would take the beetles to reproduce or even if they would reproduce in high enough numbers to make a difference. Then, in 1998 there seemed to be a sudden population explosion of very hungry beetles. Today, of the more than 5,000 acres surveyed by aerial photography, nearly half of the purple loosestrife acreage has been either munched to bare stems or damaged enough so the plants cannot flower and reproduce.

Reclamation management agronomist Wesley Green from Boise, Idaho, noted that an additional benefit of the project is that hundreds of thousands of the beetles have been transplanted to other parts of Washington and Idaho to control purple loosestrife.

Eberts cautioned that several years of defoliation are necessary to kill the plant, because this perennial weed has food reserves in its roots that can sustain it for several years. She plans to introduce another insect, a root-feeding weevil, to help deplete those reserves faster and kill more plants. Unfortunately, this weevil is slow to reproduce-taking up to 2 years from egg to adult. Cooperative research, between Reclamation and Cornell University, led to the development of a soon-to-be-patented laboratory diet that produces large numbers of healthy adult weevils in only 10 weeks.

For her work and innovations with biocontrol insects at the Columbia Basin Project, Eberts was named the Reclamation researcher of the year for 1999. While she is honored by the recognition, Eberts credits the bugs for doing much of the work.