Hungry beetles keep weed in check

Sturgeon Lake on Sauvie Island gets help from purple loosestrife-lovin’ bugs

By Steve Law

The Portland Tribune, Jun 3, 2010 (1 Reader comment)

L.E. BASKOW / Portland Tribune

Urban conservationist Mary Logalbo (left) of the West Multnomah Soil and Water Conservation District transfers leaf beetles to purple loosestrife, an invasive plant growing in the shallow waters of Sauvie Island’s Sturgeon Lake, while Oregon Department of Fish & Wildlife technician Rob Prince (right) steadies the boat. Wildlife managers hope the beetles will feast on the weed's leaves and prevent it from destroying fish and bird habitat.

Meet the beetles. Or maybe we should call them the Fab 500.

These little critters, which hail from across the ocean, love to feast on leaves of a plant called the purple loosestrife.

Purple loosestrife is tall, hardy and blooms with lovely purple flowers – and it is native to Europe and Asia.

But it’s an invasive weed in this part of the world, brought here by European immigrants in the 1800s. It has the potential to choke wetlands that are prime wildlife habitat, such as Sturgeon Lake on Sauvie Island and Oaks Bottom in Southeast Portland.

Last week, state wildlife technician Rob Prince motored out in his Mud Buddy boat to the middle of Sturgeon Lake, along with urban conservationist Mary Logalbo and her ice cream container filled with 500 leaf beetles.

The 3,200-acre lake and shoreline are home to giant sturgeon, blue herons and bald eagles. Come winter, it’s a vital stopover for migrating birds on the Pacific Flyway, attracting 100,000 ducks, 85,000 geese and 3,000 tundra swans, says Prince, who helps manage the 12,000-acre Sauvie Island Wildlife Area for Oregon Department of Fish and Wildlife.

Purple loosestrife has gained a small foothold in the lake. If it’s allowed to spread, it could sap life from the lake and easily spread to other parts of the Portland area.

“It will absolutely keep all of the other vegetation out of the area if it gets a real heavy infestation,” Prince says.

It displaces food sources for ducks and birds and clogs up waterways, making it difficult for salmon to pass.

“They really have no wildlife use. They just tend to take away habitat,” says Logalbo, who works for the West Multnomah Soil & Water Conservation District.

Each stalk of the perennial herb can produce 2 million to 3 million seeds a year. Alternatively, it can spread via its underground root system, which can have as many as 50 shoots, Logalbo says.

About the only critter that likes it are our beetles, technically two species called Galerucella calmariensis and Galerucella pusilla. They originally come from Europe and Asia, just like the purple loosestrife.

“They have a four-stage life cycle, and every stage of that they need purple loosestrife,” Logalbo says. The insect’s eggs attach to the stems. The larvae live on the bud tips. The pupae survive under the soil beneath the flowers. And the emerging adults live on the leaves.

The beetles can fly as far as six miles in search of more purple loosestrife to munch on.

After a 15-minute boat ride to the middle of Sturgeon Lake, the crew spots clumps of purple loosestrife poking up in 2.5 feet of water.

Logalbo opens up her ice cream container, where the beetles have spent the last day in a refrigerator since they were caught by net elsewhere in Oregon. One by one, she places the little guys on the purple loosestrife stalks, and the beetles instantly cling to the leaves.

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