Performance of propyzamide against black grass as a strategy to minimize selection pressure of ACCase inhibitors

Abstract

As herbicide resistance is increasing, plant protection services in Baden-Wuerttemberg and Rhineland-Palatinate conducted 15 comparable herbicide trials in order to determine the efficacy of propyzamide products against black grass (Alopecurus myosuroides) in comparison to ACCase-inhibitors from 2015 to 2017.
Depending on the resistance level, the efficacy was more stable for the DIM-herbicide Select 240 EC (clethodim) compared to FOP-herbicide Targa Super (quizalofop-P). Products containing propyzamide such as Kerb Flo (propyzamide) and Milestone (propyzamide+aminopyralid) reached a comparable black grass control. Under favourable conditions (autumn application, resistant black grass population), performance was often considerably better, but at least similar to ACCase-inhibitors. In two out of three years, a late application in early spring reduced the efficacy of black grass control by 10-20 % compared to an early propyzamide herbicide) application in autumn.
Given that application conditions were suitable, propyzamide herbicides provided reliable black grass control under various field and weather conditions. Therefore, their use should not only be concentrated on fields with herbicide resistant populations, but should be recognized as a management tool within crop rotation in order to lower selection pressure and reduce herbicide resistance development.