Weevils work on noxious weeds

The weevils have gone to work.

Through an interagency effort to control spotted knapweed, 150,000 weevils have been released over the past few weeks in the Fisher River corridor from Lake Koocanusa to the Thompson Chain of Lakes area.

“In Region 1, we haven’t done a project like this in over five years,” said Amy Grout of Montana Fish, Wildlife and Parks. “We did a small-scale project in the Flathead Valley but nothing this size with this kind of partnership. It’s all kind of new to us.”

Dan Williams of the Lincoln County Weed District indicated that the Fisher River corridor project covered considerable ground.

“This is much larger than we usually do, and to have this many cooperators is not really normal either, especially when you’re talking across the state,” Williams said. “Normally you can’t get two people to agree on anything. … It’s been really nice to work on this project.”

Two types of weevils were released – spotted knapweed root weevils and the spotted knapweed seed head weevils. The weevils specialize in consuming specific parts of spotted knapweed plants. Root weevils feed on the stems and roots of the plants. The seed head weevils consume seeds while they are still on the plant.

“Typically, you find the knapweed growing in more open areas baked by the sun – hillsides, open fields – and it’s the same thing here,” Grout said. “That’s a lot of what we found in and around the Thompson Chain of Lakes fishing access and Fisher River corridor.”

Although the bugs are expected to help the situation with the noxious weeds, it’s not an end-all solution. Such efforts often include a combination of control methods, including the use of herbicide.

“They’ve done tests with them in different states and they are fairly effective,” Grout said. “An area where we released weevils – Lone Pine State Park – I don’t know how many years ago that was but that area really doesn’t have that much knapweed now. But we were also spraying.”

Williams said weevils have been released in Lincoln County for the past five years and believes the bugs are getting the job done.

“This is our fifth year of trying to get this insect established around Lincoln County, and it’s been very successful,” Williams said. “We are seeing some good results elsewhere around the county. This area is the worst for spotted knapweed in the county, so we were happy to get the grant.”

The project received a $25,690 grant and all partners supplied matching funds for a total of about $70,000.

Joining Lincoln County and Montana FWP in the effort were the U.S. Forest Service, Montana Department of Transportation, Montana Department of Agriculture, Plum Creek Timber Co., Department of Natural Resources and Conservation, the Eureka School District and Florence High School in Ravalli.

The bug spreading began more than a month ago and continued through August. The weevils were purchased from Biological Control of Weeds of Bozeman and provided by Florence High School.

“We divvied up the bugs and everybody assisted in dispersing them and tracking things,” she said. “We’ll go back and monitor it year after year and see if it’s a successful tool to use.”

In Grout’s case, Montana FWP first went out on Aug. 6 and then again during the last week of the month.

“We covered the ground pretty well out there,” Grout said. “We’ll see how they do. Fish, Wildlife and Parks is looking for alternatives – another tool in the toolbox to use because it’s just so hard to get out there and spray chemical. You have to have the right weather conditions, the right equipment.”

Apparently, the bugs will easily stick to people and clothing.

“When we were releasing them, they kind of have burrs on their feet,” Grout said. “They stick to you and they were climbing all over us.”

But it’s the spotted knapweed – not humans – that these bugs are interested in. And Grout said Montana FWP is looking at using weevils as part of other projects.