In the battle against noxious weeds, the warriors are tiny beetles with healthy appetites.
And the battle in this area is being raged on a rolling hill near the Brainerd-Crow Wing County Airport. At issue is an aggressive, exotic perennial weed called leafy spurge that is choking out native grasses and taking over entire fields.
Leafy spurge looks nice from a distance with its spike-like leaves and yellow flowers. But the plant contains irritating chemicals that make leafy spurge a diet avoided by cattle and horses.
With other native grasses unable to compete with the foreign invader, land that sustained grazing and wildlife is less able to do so. The U.S. Department of Agriculture estimates losses of more than $100 million in the nation, largely in the northern Great Plains, West and northeast, because of the weed. Chemical control has been an expensive option on the hardy plant and one that has its own collateral damage.
That is where the beetles step in -- on all six legs. They are considered biological controls, or a way to use nature in a fight. They can jump and fly, attacking the plant as larvae and adults. About the size of a colored ball on a straight sewing pin, the quick jumping beetles resemble fleas. Hence their common name -- flea beetles.
About 70,000 of the beetles were released near the Brainerd-Crow Wing County Airport last summer. A large concentration of leafy spurge had taken over a small rise on the airport property. Mark Rudningen, Crow Wing County agricultural inspector, recently visited the area to collect beetles for a state analysis. He liked what he found.
Obvious stress signs, brown spots and unhealthy looking plants, were readily visible in sections. Rudningen collected beetles by dragging what looked like a white windsock among the plants. Unlike butterfly nets, the sock is solid and the white materials allowed for easier identification of the tiny insects.
"In Europe they don't have this problem because the plants have so many natural enemies," Rudningen said as he looked for beetle specimens among grasshoppers and ants caught in the sweep. But the foreign plants are without natural controls in the U.S.
The beetles, imported mainly from Europe, were heavily tested against crops -- including corn and soy beans -- to confirm they would not create havoc with farm fields. Mortality studies find the beetle hardy with an ability to winter underground and produce more numbers each year. Flea-beetle females lay an average of 250 eggs in a season.
"What we are trying to do here is establish an ancestry," Rudningen said. "That's my goal."
That goal would allow Crow Wing County to be a producer of the beetles with collections at the right time of year gathering hundreds or thousands of the tiny insects for use in other areas.
The progress is visible, but biological controls take time to work. And Rudningen said herbicides, mowing and mosquito controls such as spraying are harmful to the working beetles.
Rudningen said he would like to work with private landowners to control the noxious weed with the beetles. A recent beetle release put the insects to work at the Northland Arboretum. Such releases are recorded and tracked with the Department of Agriculture.
"This is something you don't notice over night," Rudningen said of the beetle's progress in the weed war. "It's a means to control this weed without using herbicides ... and it looks like it is working."
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