Improving the herbicidal activity of mesosulfuron-methyl oil dispersion against Aegilops tauschii by decreasing particle size and adding adjuvant polyvinyl alcohol

BACKGROUND Mesosulfuron-methyl (MSM) is currently the only available selective herbicide for controlling Aegilops tauschii in wheat fields. Improving the control performance of MSM against Ae. tauschii is crucial for ensuring wheat yield. Herein, strategies to improve the bioactivity of MSM against Ae. tauschii and the underlying mechanism were investigated. RESULTS The efficacy of MSM oil dispersion (MSM-OD, GR 50 = 21.62 g a.i. ha −1 ) on Ae. tauschii was higher than emulsion in water (GR 50 = 59.96 g a.i. ha −1 ) and emulsifiable concentrate (GR 50 = 77.34 g a.i. ha −1 ). A greater retention on Ae. tauschii leaves was responsible for the increased MSM-OD bioactivity. As the particle size decreased from 13.58 to 1.20 μm, the herbicidal activity of MSM-OD towards Ae. tauschii increased 3.07-fold, which was attributed to the small particle size-enabled faster plant absorption of MSM. Polyvinyl alcohol (PVA, 3%) addition in MSM-OD with a small particle size (MSM-OD-S + PVA) increased MSM residue on Ae. tauschii leaves after washing, and thus herbicidal activity. The increased wettability on Ae. tauschii leaves was related to the PVA-induced rainfastness increase of MSM-OD-S. Importantly, MSM-OD-S + PVA at the recommended field rate did not show an adverse effect on wheat growth. CONCLUSION A suitable formulation, reduced particle size and PVA addition can increase the herbicidal activity of MSM against Ae. tauschii , particularly under rainy conditions. These results can provide guidance for the development and application of other herbicides. © 2025 Society of Chemical Industry.