The Washington Department of Fish and Wildlife (WDFW) is releasing insects to control weeds on eastern Washington wildlife areas and cooperatively-managed private properties.
Department land managers are working with Washington State University experts on the biological weed-control program. Like other biological-control methods, the weed-devouring insects reduce the need for chemicals. They have been tested to ensure they do not pose a threat to native wildlife or desirable vegetation.
"These releases are part of our continuing effort to use the best ideas and best-available science in caring for lands that we manage or help manage," said Mark Quinn, WDFW's lands manager.
WDFW crews recently released 7,000 stem-boring weevils (Mecinus janthinus) on the Wells, Sagebrush Flat and Swakane wildlife areas in Okanogan, Douglas, and Chelan counties to control Dalmatian toadflax (Linaria dalmatica), an invasive, exotic plant that crowds out native vegetation. Another 2,200 weevils were released by WDFW on private lands managed under cooperative agreements in Douglas County. In addition, 4,600 insects were released by the Foster Creek Conservation District on farms and ranches in northern Douglas County.
As their name implies, the stem-boring weevils chew through the stems of toadflax, in which they overwinter and lay eggs, killing the weeds. The tiny weevils are black, up to an eighth of an inch long, and have a curved snout. The weevil originally was imported from Europe to Canada and has dispersed into Stevens County.
Most of the Mecinus weevils were purchased from Washington State University (WSU) through Dr. Gary Piper, a WSU entomologist who specializes in biological weed control and integrated pest management. Seven hundred weevils were provided to WDFW and 2,600 to Foster Creek Conservation District free of charge by the Quad County BioControl Project headquartered in Ferry County. So far WDFW has spent $4,300 on the Mecinus weevil effort from its wildlife area and noxious weed control budgets.
According to Piper the newly-released insects generally take two to three years to form colonies large enough to have a visible effect in reducing the number of the weeds. The introduced insects were extensively tested by federal and state authorities before they were approved for use as biological weed control.
Ron Fox, a WDFW wildlife biologist based in Wenatchee, notes there have been other significant biological-control efforts throughout eastern Washington.
"The level of interest in biological weed control has been extremely high from landowners who participate in our cooperative agreement program," Fox said. "Most of them are eager to be involved in the insect releases and we have more requests for the bugs than we could supply."
One of the toughest exotic, invasive weeds in Washington, diffuse knapweed (Centaurea diffusa), has been successfully repressed at WDFW's Sinlahekin Wildlife Area in Okanogan County with the release of another European insect, the knapweed flower/seedhead weevil (Larinus minutus). The Colockum, Chelan Butte, and Chilliwist wildlife areas in Chelan and Okanogan counties have received a total of 1,500 Larinus weevils and another 1,500 were released on Douglas County private lands in WDFW cooperative-agreement programs. Additional releases of the knapweed weevil are planned this month on the Colockum Wildlife Area.
The golden loosestrife beetle (Galerucella pusilla), another European import, has been released to control purple loosestrife (Lythrum salicaria) at the Washburn Island management unit of WDFW's Wells Wildlife Area and other sites in the Columbia Basin.