Thursday, March 28, 2024

Bridgeport students help monitor battle between bad weeds and good bugs

“They work 24 hours a day, seven days a week, they’re self-perpetuating.”

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As landowners in North Central Washington are all too painfully aware, knapweed is an all-around nasty weed. It first arrived from Eastern Europe in alfalfa seed in 1907, and it's been causing trouble ever since-choking out native plants, presenting a fire hazard, damaging the nutrients in the ground; it can be toxic to livestock if they eat enough. And ever since it first established itself landowners have been trying to get rid of it.

Students at Bridgeport High School are involved in a project to see how the plant's natural enemies can be turned against it. Students in the high school's advanced biology classes released some colonies of knapweed seedhead weevils in a field full of knapweed in June, and biology students are going to monitor what happens to that field over the next three or four years.

The biology classes got involved in "biocontrol," as the practice is called, because of a presentation to the Bridgeport City Council last fall. High school science teacher Calvin Stark was at the council meeting when Dale Whaley, who works for WSU-Douglas County Extension, talked about biocontrol and how it works when the enemy is knapweed. Stark said he invited Whaley to talk to his biology class about biocontrol.

Knapweed is not a big problem in its native range, Whaley said, because it has enemies, i.e., bugs. Diffuse knapweed and spotted knapweed are among the preferred foods of the knapweed seedhead weevil.

The adult weevils eat the knapweed plant itself, Whaley said, starting with the emerging knapweed rosettes and moving on to the leaves and stems as the plant matures. When the knapweed starts making seeds, female weevils start laying weevil eggs in the seed heads. The weevil eggs hatch into weevil larvae that eat the seeds and use the cleaned out seed pod as nest; they mature into adult weevils, feed on the knapweed until winter comes and spend the winter in the ground. When spring comes the adults emerge and start feeding on any knapweed that raises its nasty green head. The cycle starts again. Eventually the knapweed loses. It's a relatively slow process-combating an infestation with weevils takes three to five years, Whaley said.

The idea is to reduce the vitality of the knapweed plants and the size of the infestation to shift the balance back to more beneficial plants, he said.

The bugs have some advantages over other methods of control, Whaley said. They can be used in any kind of terrain; "they can get to areas we can't." Supervision is just a matter of checking the site. "They work 24 hours a day, seven days a week, they're self-perpetuating," Whaley said, and they only eat knapweed. "When they run out of knapweed in the area where they're released, they'll just go find more knapweed," Stark said.

That's kind of important, because there are cases of biocontrol gone bad-there was the unfortunate incident back in the late 1960s and early 1970s with bugs that ate Canada thistle, which had become an enormous pest all across the country. Unfortunately the bugs that loved Canada thistle also loved other, beneficial plants; at the time, Canada thistle was such a big problem-and concern about threatened and endangered species was much less acute-that the benefit was deemed worth the risk to native plants. Whoops. The bugs killed the Canada thistle, all right, but they also killed plants wildlife officials wanted to save.

As a result, federal and state authorities "really cracked down" on host-specific biocontrol projects, Whaley said. Currently it can take up to 10 years to get a bug approved for release; the research and testing can cost anywhere from $2 million to $5 million. "We don't want to bring in another pest," Whaley said.

Knapweed seedhead weevils were first released in Washington in 1990.

Bridgeport has its share of knapweed, including a nice little patch on a vacant lot not far from the high school. Stark said he thought a knapweed biocontrol project of some kind would be a good project for his biology classes. Some of his students are already collaborating with the Foster Creek Conservation District; "our kids go out and help them with projects," Stark said, monitoring test sites and helping with test projects. (It's part of the "Student Achievement from the Ground Up" grant, which also involves students in Quincy, Waterville, Oroville and Tonasket. The grant was awarded through the Woodland Park Zoo and the Washington Nature Conservancy.)

Stark said he invited Whaley to come to talk to the environmental science class, and "the kids really thought that this was kind of cool stuff." But it couldn't be pursued until the spring, when Stark and his students in advanced biology enlisted the help of science teacher Eric Schmidt and his biology class. The students released the bugs in the field near the high school and will help monitor the site over the next three to four
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