Russian thistle (Salsola tragus) and kochia (Kochia scoparia) are common annual broadleaf weeds that become “tumbleweeds” in the fall. These plants can be problematic in many situations where the soil is highly disturbed. These annuals can produce thousands of seeds per plant. The best form of control is to prevent the plants from going to seed. If populations are intensively managed for two to three years to prevent seed production and no new weeds blow in, the weeds can be eradicated as the seeds are short-lived, most are only viable for 1-2 years after production. Mowing can be effective on smaller plants. Tillage and hand hoeing can control both seedling and larger plants as the plants have shallow root systems.
Pre-emergent herbicides can provide some season-long control. Post-emergent applications are also effective if made when plants are small, less than 4 inches in diameter. Labeled post-emergent products include 2,4-D and combinations, dicamba, glyphosate, triclopyr, and pendimethalin. Often post- and pre-emergent herbicides are mixed together to provide control of established weeds and repeated flushes of seed germination. Maintain the area with alternate species to reduce bare soil. Other plants will outcompete new weed seedlings.
For more information, see the following Colorado State University Extension fact sheet(s).