MOIESE — The thumping of tubs and whipping of toadflax signaled the start of the National Bison Range’s great weevil roundup of 2017.
Within minutes, more than a thousand of the little black bugs had been knocked from their leafy hideouts and tucked into waiting coolers, not to be mixed up with the other coolers full of soda for the volunteer wrangler crew.
About 40 people gathered by the Montana Noxious Weed Trust Fund spent Wednesday morning literally beating the bushes on the far western edge of the 18,000-acre range for Mecinus janthiniformis, which loves to eat and lay eggs in Dalmatian toadflax. It may be the only thing that appreciates toadflax.
“This way the range staff can get a bunch of biocontrol done in one day,” Melissa Maggio-Kassner told the volunteers at the start of the effort. “We should be able to collect about 20,000 bugs," which will be deployed against other toadflax infestations on the refuge.
Dalmatian toadflax and its cousin, yellow toadflax, came to the United States from southern Europe and Asia hundreds of years ago. While they have pretty yellow flowers, they also grow and spread uncontrollably. They outcompete native plants for water and soil nutrients, and produce scads of seeds that can lie dormant for 10 years (most native seeds only remain viable for two years). Bison don’t graze on it, while elk and antelope only nibble the tops off without slowing it down.
“We feel that the toadflax just laughs and thumbs its nose at us,” Revais Creek resident Sally Baskett said of her efforts to stop the weed from invading all of her property near the Bison Range. “We’ve even tried hard blasts of herbicide. It’s very expensive and time-consuming. And this is a banner year.”
And the problem may get worse. Dalmatian and yellow toadflax can cross-pollenate, creating a hybrid that’s both hardier and harder to control. Colorado State University plant geneticist Sarah Ward explained that while the Dalmatian variety was common in Eastern Europe, the yellow species grew mainly in Great Britain.
“Once they were introduced in North America, they met, fell in love and had babies,” Ward joked. “And they are not populations that come and go. If I may say so, these things kick ass. They outperform the parents.”
The first hybrid toadflax was detected near Radersburg, Montana, in 2005. Since, it’s been reported in Colorado, Idaho, Washington and Wyoming. The new version can be hard to separate from the yellow version, unless you look at their seeds.
“The Dalmatian seeds look like flying saucers, while the yellow toadflax seeds looks like Brazil nuts,” Ward said. “The hybrid seeds look like Brazil nuts with wings.”
To control invasive toadflax without chemicals, you need an exotic bug that targets it while ignoring more popular or valuable plants. Montana State University Professor Robert Nowierski brought the first Mecinus weevils from Switzerland. We’ve since discovered that while Mecinus janthiniformis likes Dalmatian toadflax, we need Mecinus janthinus weevils to fight yellow toadflax. And no one’s sure which weevil might take on the hybrid toadflax.
Fortunately, the hybrids haven’t made an impact on the Bison Range yet. Wednesday’s biggest challenge was keeping the captured weevils from blowing out of the tubs in the breezy morning. The volunteers fanned out on hillsides, gently whipping toadflax stems and knocking the weevils into their tubs. A couple hundred weevils would fill a whisky shot glass.
“It’s been a really amazing success story for biocontrol in Montana,” said volunteer collector Tracy Sterling, who came over from Bozeman to help with the roundup. “Growers know about it. High school kids know about it. It works.”