Spotted knotweed is a prohibited noxious weed in Minnesota. Reporting to the state is important. Cultural control, digging out, is one method of removal. Animals will not eat knapweed. The state does have a biological control (insects) program for property owners. I have placed links below with additional information about spotted knapweed. The last link contains information about the state biological control program. 

https://extension.umn.edu/identify-invasive-species/spotted-knapweed

https://www.dnr.state.mn.us/invasives/terrestrialplants/herbaceous/spottedknapweed.html

https://www.mda.state.mn.us/plants/pestmanagement/weedcontrol/noxiouslist/spottedknapweed/knapweed