First report: spotted knapweed (Centaurea stoebe) resistance to auxinic herbicides

Spotted knapweed is a prohibited noxious weed that is primarily controlled with auxinic herbicides. A population collected from a managed rangeland in East Kootenay, BC, was highly resistant to both clopyralid and picloram, with R/S ratios of >25 600 and 28, respectively. This is the first report of resistance in spotted knapweed.

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