'Noxious' spotted knapweed has made its way to southwest Missouri, experts say

Sara Karnes
Springfield News-Leader
Spotted knapweed (a relative of the various thistles) has been tabbed a noxious weed in several western and northern states.

A potentially invasive weed has been showing up in the southwest region of Missouri, and University of Missouri is reminding folks to be on the lookout. 

David L. Burton, with University of Missouri Extension Office, shared more about the weed known as spotted knapweed, which is a relative to various thistles. It has been noted as a "noxious weed" in several western and northern states.

Nearly two decades ago, the extension's agriculture specialists began informing the public about spotted knapweed.

“As word got out, more and more areas reported the bad, but very attractive knapweed plant was quite widespread,” said Eldon Cole, a livestock specialist with MU Extension.

Missouri Department of Transportation and the Department of Conservation consider the weed an "invader that we need to jointly wage war on," according to Cole.

Spotted knapweed (a relative of the various thistles) has been tabbed a noxious weed in several western and northern states.

Spotted knapweed blooms in June to early July before sprouting a rosette.

“Of course, as we observed how widespread it was, the logical question was how did it come to arrive here and how can it be controlled?” Cole asked.

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Highways, railroad right-of-ways and excavation sites was the more likely of the culprits.

“It became apparent there was a connection between that soil disturbance and the beautiful pink flowered weed that appeared in a year or so,” Cole said.

Similar to thistles, spotted knapweed can be controlled by timely herbicide treatment in fall or spring, Burton writes. Knapweed weevils have also been successful when used. In 2008 and 2009, two different species of knapweed weevils were released in specific areas of heavy knapweed infestation.

Spotted knapweed (a relative of the various thistles) has been tabbed a noxious weed in several western and northern states.

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Over the years, Cole said there has been progress in reducing the spread of spotted knapweed where weevils were released and herbicide treatment.

Some of the weed still is able to spread through hay harvest and transportation of it to new feeding areas. Cole says people should take care to not spread seed from infested fields to clean ones with equipment.

Knapweed was added to Missouri’s noxious weed list in 2008.  

Sara Karnes is an Outdoors Reporter with the Springfield News-Leader. Follow along with her adventures on Twitter and Instagram @Sara_Karnes. Got a story to tell? Email her at skarnes@springfi.gannett.com.