The Synergistic Effect and Mechanism of Different Adjuvants on Pinoxaden Efficacy Against Lolium Multiflorum Lam.

Adjuvants play a crucial role in optimizing and improving the efficacy of herbicides. Therefore, adding appropriate adjuvants to herbicides is an important part of weed control. The aim of this study was to investigate the synergistic effect and underlying mechanism of action of three commercial adjuvants (Hasuteng, Penwubao, and Zhenxiao IV) in conjunction with pinoxaden for controlling Lolium multiflorum Lam. The results of synergic effect, which were determined by dose-response assay showed that the addition of Hasuteng and Penwubao could significantly enhance the efficacy of pinoxaden and decrease the ED50 50 (the herbicide dose resulting in 50% weed control) on L. multiforum while being safe to wheat. Hasuteng and Penwubao were further selected to investigate the underlying mechanisms by which adjuvants enhanced the efficacy of pinoxaden. The results indicated that the addition of Hasuteng and Penwubao significantly reduced the surface tension and shortened the drying time of the pinoxaden solution; moreover, it significantly increased both expanded diameter and maximum retention. Additionally, ultra high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) analysis was used to evaluate the recovery rate, absorption level, and rainfastness. These two adjuvants could improve the absorption and metabolism levels of L. multiforum to pinoxaden. However, Hasuteng and Penwubao did not improve the rainfastness of pinoxaden. In summary, Hasuteng and Penwubao enhance the efficacy of pinoxaden by improving its physical properties and absorption level. The studies present a novel approach for enhancing the utilization rate of pinoxaden and provide theoretical guidance toward effectively reducing herbicide application in wheat fields.