The first infestations recorded in Montana were in the central part of the state in Judith Basin County near Stanford in 1958, in Park County in 1970 and in Fergus County in 1984. The largest infestation of yellow mignonette in Montana occurs in the Judith River drainage of Judith Basin County. This infestation most likely started in a hay field in the 1950s. Root segments and crown tissue detached from parent plants and relocated by tillage implements readily form new roots and shoots. The remaining intact root regener ates numerous shoots near the cut end in response to tillage giving a witchbroom appearance to the newly emerged plant'.
Hand pulling or digging is effective only if the entire root is removed.
The large primary root tends to break when pulled rather than remaining intact. The remaining root system has sufficient nutrient reserves to support regenerative shoot growth from considerable depths. When the root system in the top 40 cm of soil was removed, the remaining root system regenerated plants within a year. Metsulfuron has shown excellent selective activity against yellow mignon ette in wheat and barley and has been used successfully as a spot treatment along roadsides. Extensive mapping of yellow mignonette in Judith Basin and Fergus counties was completed and will be used to monitor its spread and the success of the control project.