MU combats spotted knapweed
MU is funding a project to combat the species.
Published Sept. 1, 2009
MU and the Missouri Department of Transportation are teaming up to eradicate spotted knapweed, an invasive plant species located throughout southern Missouri.
Last year, MU's Plant Protection Program administered a $4,200 grant to the MU Extension Office in Barton County for the purchase and distribution of biological controls to stem the outbreak.
Tim Schnakenberg, an agronomy specialist with the University of Missouri Extension in Galena, said spotted knapweed was discovered 10 years ago along roadsides in the southwest part of the state. Since then, he said, it has spread into agricultural fields after mistakenly being included in bales of hay.
"Spotted knapweed tends to dominate other vegetation and crowd everything else out after it gets a foothold," Schnakenberg said.
The weed possesses a toxic chemical called catechin, he said, which is released into the soil and kills other plants. Because it is non-native, or alien, to Missouri, it has few natural predators, allowing it to spread quickly.
The Missouri Legislature designated the plant as a noxious weed in February 2008, adding that it could cost $35 per acre to control. Aside from presenting economic problems to the agricultural industry by spoiling grazing sites, it can significantly lower property values should it reach metropolitan areas. Schnakenberg said the weed is not yet an issue in St. Louis or Kansas City, but MoDOT is monitoring the situation.
"Currently, the spotted knapweed problem is such a large-scale problem in south Missouri that it is beyond the scope of herbicides to control it," said Tim Banek, Invasive Species Coordinator at the Missouri Department of Conservation. "Therefore, the next step in fighting a noxious weed is to introduce its natural enemies."
Banek conferred with other experts and concluded the root weevil and the seed head weevil would control the spread of the spotted knapweed in Missouri. After being in the United States for 30 years, these insects have proven to be host-specific, or only affecting the spotted knapweed.
The insect supplier Weedbusters Biocontrol's Web site stated the root weevil is very effective, laying its eggs on the crowns of the spotted knapweed's roots. The larvae then burrow into the root and prevent the transportation of water and nutrients, effectively killing the plant.
The seed head weevil consumes the plant's seeds, weakening its chances for spreading.
Weedbusters Biocontrol owner Bob Rich, whose company is based in Montana, said biological controls are effective at combating the invasive species.
"Spotted knapweed's a tremendous environmental threat and these biological controls have really done an excellent job here and present no collateral damage that you get with herbicides," Rich said.
The MU Extension Office spent $3,200 on weevils and the remainder on transportation costs for dispersing the insects around southern Missouri.
Assistant Professor Emeritus of Entomology Ben Puttler said since the program started last year, MU has released approximately 4,500 weevils. MoDOT has placed 25,500 weevils and the MDC, 1,500.
Although the insects are dispersed, Puttler said there is no guarantee they will establish themselves in the new habitat.
"We might not see recoveries in these areas for two and three years," Puttler said. "The good news is that we've seen recovery at two sites. There's an indication they are establishing themselves in Missouri."