Russian thistle (Salsola tragus), also known as tumbleweed, is a persistent summer annual weed and an ongoing challenge for wheat growers in Eastern Oregon. The weed infests nearly 5 million acres across the Pacific Northwest, costing farmers more than $50 million each year in management.
By advancing effective alternatives to glyphosate and promoting integrated management, Oregon State is helping protect the productivity and sustainability of Oregon’s wheat industry.
Severe infestations can reduce wheat yields by up to 50% and, in some cases, prevent harvest entirely. Each plant produces more than 40,000 seeds that spread after frost, quickly replenishing the soil seedbank.
In no-till systems, where herbicides are the primary tool for weed control, resistance to glyphosate leaves growers with fewer options for managing this prolific species.
Oregon State University Extension researchers and agronomists partnered with growers to identify alternatives to glyphosate and expand integrated weed management strategies. From 2014 to 2017, large-scale trials in Morrow County showed that the residual herbicide sulfentrazone could effectively control Russian thistle.
Oregon State research and Extension outreach led to regionwide adoption of sulfentrazone for Russian thistle control. By 2021, an estimated 30,000 acres were treated and protected from the yield losses due to Russian thistle and other broadleaf weeds that sulfentrazone controls as well. Based on an estimate of five bushels per acre at $7, the sulfentrazone application saved more than $1 million in wheat yield.
This work led to a three-year, multi-state study with Washington State University, which confirmed sulfentrazone as a reliable option in no-till fallow systems.
Further studies published in Weed Technology (2023) and Weed Science (2024) examined Russian thistle emergence, seed viability and seed longevity in wheat rotations. Results showed that most seedlings emerge in the first year after dispersal, with seed production peaking in September.
Early emerging plants had more biomass and seeds than later emerging plants and plants growing in fallow (without competition) developed bigger than when growing in crop (with competition). These findings underscore the importance of early-season control, and the maintenance of competitive wheat stands.
At the same time, Oregon State researchers tested additional herbicide options. Trials showed that flumioxazin + pyroxasulfone (Fierce) provided strong residual control. Tank mixes of glyphosate with tiafenacil (Reviton) or pyraflufen (Vida) delivered effective postemergence results.
The studies also provide growers with science-based strategies to manage resistant populations through diversified herbicide programs, crop competition and timely treatments.
By advancing effective alternatives to glyphosate and promoting integrated management, Oregon State is helping protect the productivity and sustainability of Oregon’s wheat industry. This work equips growers with practical tools to reduce yield losses, sustain no-till systems that conserve soil and water, and strengthen farm resilience across Eastern Oregon.
This research was supported by the U.S. Department of Agriculture Agricultural Research Service under agreement no. 58-2074-2-003, as part of the Pacific Northwest Herbicide Resistance Initiative.
It was also funded by the USDA National Institute of Food and Agriculture (project no. ORE00339) and partially funded by the USDA-NIFA Hatch Project (no. 1017286) and by an endowment from the Washington Grain Commission.