Smooth scouringrush is a deep-rooted, rhizomatous, herbaceous perennial that has been difficult to control in dryland wheat-producing regions in the Pacific Northwest. Long-term field experiments were conducted at Omak, Edwall, and Steptoe, WA, to evaluate herbicide sequences with chlorsulfuron + metsulfuron (21.9 + 4.4 g ai ha-1), triasulfuron (29.5 g ai ha-1), or MCPA ester (780 or 1122 g ae ha-1). The Omak trial (2017-2021) included two 2-year cycles of a winter wheat/chemical summer fallow rotation. The Edwall and Steptoe trials (2019-2025) included two 3-year cycles of winter wheat/spring wheat/chemical summer fallow rotation. Six pre-assigned herbicide sequences tested efficacy of 1) chlorsulfuron + metsulfuron applied in one or both chemical fallow phases and 2) triasulfuron applied only in wheat. MCPA ester was applied as a check treatment. Smooth scouringrush stem density was evaluated in each plot each year. Chlorsulfuron + metsulfuron applied in the first chemical summer fallow phase maintained relatively low stem density in all three trials through the first rotation cycle compared with the check treatment. Chlorsulfuron + metsulfuron applied in the second chemical summer fallow phase extended control through the second rotation cycle. However, in the 3-year rotation trials, chlorsulfuron + metsulfuron was not as effective in the second rotation cycle at Steptoe where stem densities only averaged 6 stems m-2 at time of the second application. Triasulfuron applied in wheat was not effective in controlling smooth scouringrush. Smooth scouringrush reduced wheat yield in the MCPA ester check sequence at Edwall, but no differences were observed at Steptoe or Omak. Chlorsulfuron + metsulfuron applied in chemical fallow is effective for long-term control of smooth scouringrush in wheat-based cropping systems. A subsequent application in chemical fallow can be effective if there are an adequate number of stems present to facilitate foliar uptake.