OSU works to delay glyphosate resistance in Russian thistle

Judit Barroso, an OSU assistant professor and Extension weed specialist, is the co-author of the Extension publication "Russian Thistle: Management in a Wheat-Fallow Crop Rotation."

Russian thistle, also known as tumbleweed, causes serious crop production problems in dryland small-grain producing areas in the United States, costing farmers more than $50 million annually in control measures. Russian thistle breaks off the stem when it dies and moves with the wind. As a tumbleweed, it can spread seeds over long distances. Each plant, growing without competition, produces more than 50,000 seeds.

Farmers in the arid region of northeastern Oregon rely on repeated applications of herbicides such as glyphosate to control Russian thistle. In the fall of 2015, they reported difficulties in controlling Russian thistle with glyphosate, one of the most widely used herbicides in the United States. The following February, OSU researchers randomly collected 10 Russian thistle populations on fallow fields in Umatilla, Morrow and Sherman counties. Lab testing of the samples showed that three of the collected populations in Morrow County were glyphosate-resistant.

In 2017, the need to identify alternative management practices for the weed was a top priority for Judit Barroso, Oregon State University assistant professor, and OSU Extension agent Larry Lutcher. Lutcher, a wheat production specialist, and Barroso, a weed scientist, conducted field trials on alternative herbicides and presented integrated weed management practices during grower meetings, field days and tours. Wheat producers are adopting new strategies as they learn more about possible alternative practices that address this critical problem, especially in lower rainfall areas.

Their research resulted in the Extension publication, "Russian Thistle: Management in a Wheat-Fallow Crop Rotation."

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