MANHATTAN, Kan. (AP) — Kansas State University researchers say new research helps explain why an invasive weed is developing resistance to a well-known herbicide.

The researchers found that the plant kochia (KOH’-sha) has evolved to have multiple copies of a gene that targets the weed killer glyphosate, allowing it to survive treatment. Monsanto brought glyphosate to the market in 1976 under the name Roundup.

Assistant agronomy professor Mithila Jugulam says the resistance mechanism is becoming prevalent in other glyphosate-resistant weeds. Jugulam says the resistance evolved as the result of continuous use of glyphosate and the lack of herbicide diversity in controlling this weed.

The journal Plant Physiology recently published the study Jugulam worked on with plant pathology professor Bikram Gill.