A tiny weevil from the other side of the world could help control a plant that is overrunning much of the West.
About 300 of the creatures were dumped out of a cardboard container near the Coeur d’Alene Airport Monday afternoon. Although scientists and government officials have high hopes for the bugs, their release into the weedy wilds of North Idaho came with little ceremony or television cameras.
Then again, high drama is not typically associated with insect introductions. The weevils didn’t even seem to care about their newfound freedom. Most just clung to their paper towel home.
“They’re quite relaxed,” observed Mark Schwarzlaender, a biological control expert from the University of Idaho. “It must be the cool weather.”
With warmer temperatures and a bit of luck, the larinus weevils will breed and begin chewing tiny holes into the flowers of spotted knapweed. Within five years, there should be enough of the insects to begin taming the field of weeds, Schwarzlaender said. Eventually, the weevil offspring will begin flying to nearby spotted knapweed stands.
The insects won’t be facing famine anytime soon. Just about every vacant lot, alleyway or neglected piece of dirt in the West has become home to knapweed, which is distinguished by its spiky, blue-green stems and purple flowers. The Eastern European plant crowds out native grasses and shrubs and is completely inedible to wildlife and livestock. One plant can produce 25,000 seeds.
Chemical herbicides kill the weed, but other nearby species are also affected, Schwarzlaender said.
Knapweed seeds will be returned quickly to the land and won’t have difficulty overtaking the natives. The best hope for a long-term fix is by relying on thousands of years of evolution.
In Eastern Europe, knapweed grows smaller and is less of a problem because insect predators have kept the plant in check, Schwarzlaender said.
In North America, the plant has flourished because it has no enemies.
More than a dozen flies, weevils, moths and beetles have been brought from Europe to fight the weed, but the flower-boring larinus weevil appears to have some of the greatest potential with the least risk, Schwarzlaender said.
The weevils were released at the Coeur d’Alene Airport and about 15 other North Idaho locations by students who participated in a free weed control class taught by Schwarzlaender. The class continues today with a focus on another dangerous invader: dalmatian toadflax. Everyone who attended Monday’s session was given a container with 300 hand-counted weevils.
Education is important, Schwarzlaender said, but “the major goal of the workshop is distribution of the weevils. To reach the private landowners like this is just so fantastic.”
Irv and Carol Jenkins intend to set their bugs free on their 11 acres along Lake Pend Oreille near Sagle, Idaho. “We’d much rather not use any chemicals being near the lake,” Carol Jenkins said.
Scientists have been sprinkling potentially dangerous bugs on knapweed without much success since the 1960s, Schwarzlaender said. It wasn’t until after the fall of the Iron Curtain that answers were gained into why knapweed in the United States was largely unaffected by the bugs that chewed on knapweed in France and Germany. “Turns out it was a different plant species,” Schwarzlaender said.
Some of the newest weevils were released in parts of North Idaho in the 1990s. Because it takes up to five years for a population to become established, it’s difficult to tell how successful the program has been, said Carol Randall, a forest entomologist with the Idaho Panhandle National Forests. Most of the changes have been subtle and difficult to measure. Much is dependant on the weather.
“Patience is a virtue when it comes to biological control,” Randall said. “We’re seeing some shifts in the population. I do firmly believe biological control is reducing the population of spotted knapweed in this county.”
About 16,000 weevils were also released last year in Pend Oreille County, Wash., said Jan Rice, a member of the county’s weed control board. Rice and a colleague attended Monday’s class in Coeur d’Alene. A small network of biological weed control officials is being developed across the region to help target the worst weeded areas.
“The more coordinated efforts are beginning to speed up the results,” Rice said.
The weevils weaken the plant by boring holes into the flowers and laying eggs. The larvae feed off the flower stem. Other weevils that bore into the plant’s root are also being studied.
Years of testing and research are required before releases are made to ensure the weevils do not also have a taste for other plants, especially crops, Schwarzlaender said.
Extensive studies are also conducted to ensure the bugs will not mutate anytime soon — modeling conducted by ecologists has predicted the larinus weevils need another 500,000 years before they will change enough to begin chewing on other plants, Schwarzlaender said.
“We are very excited about these weevils,” he said.
The weevils have already helped knock down thick stands of knapweed in parts of Oregon and Montana, Schwarzlaender said. About the only unintended side effect, to date, has been a spike in the number of deer mice. Weevil larvae are an easily accessible source of protein. There’s some speculation this boost could also cause a rise in hantavirus, which is carried by deer mice.
The weevils have proved especially effective in steep, hard-to-reach areas. This will make them useful in much of North Idaho, said Judd Reed, the roadside vegetation foreman for the Idaho Transportation Department in Coeur d’Alene. “We’ve got areas we can’t spray. It’s too expensive, and we can’t always pack in enough hose.”
Knapweed’s success in Kootenai County is partially due to the region’s transformation from farm field to housing developments.
The plant is actually harmed by nitrogen fertilizer, which meant it was largely kept under control by farming practices, said Nina Eckberg, the county’s noxious weed superintendent.
State law requires all property owners to control weeds, but many newcomers have difficulty understanding the threat of knapweed.
The development has also been harmful to at least one population of the released weevils. Last year, a church was built on a weedy lot in Coeur d’Alene that was also one of the first weevil release sites, Eckberg said. “They bulldozed the population.”
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