Response of invasive perennial western ragweed (Ambrosia psilostachya) to chemical and mechanical control

Western ragweed (Ambrosia psilostachya) is an invasive species in spring‐sown crops that can also cause allergic rhinitis and asthma due to its allergenic pollen. In order to evaluate the chemical and mechanical control of western ragweed, two separate experiments were conducted in 2019 and 2020. Chemical treatments included non‐treated plots, the combination of glyphosate and 2,4‐D, glyphosate + ammonium sulfate, bentazon, imazethapyr + surfactant, picloram, 2,4‐D, and mechanical treatments included: once mowing at 3–4 leaf stage, once mowing before male flowers' emergence, once mowing early female flowering stage, two mowings at 3–4 leaf stage, two mowings before male flowers' emergence. Results of these studies indicated that in both years, picloram at 0.96 kg ai ha−1 and the combination of 2,4‐D and glyphosate at 1.23 + 0.72 kg ai ha−1 provided more than 90% control of western ragweed and reduced plant height, dry weight, and density. The application of imazethapyr and bentazon, respectively, at the rates of 0.1 and 0.96 kg ai ha−1 did not cause visual damage. The mowing shortly before flowering was the most effective mechanical treatment for western ragweed control. In order to the efficient management of the western ragweed, we suggest that the mowing treatments if appropriately timed and application of glyphosate plus 2, 4‐D at 1.23 + 0.72 kg ai ha−1, and picloram at 0.96 kg ai ha−1 can prevent western ragweed from spreading by suppressing growth and reducing seed production.