Julius-Kühn-Archiv (Feb 2022)
Management of herbicide resistant weeds in a crop rotation with an Acetolactat-synthase-inhibitor tolerant sugarbeet variety
Abstract
ALS-resistant weeds are of major importance in many European agriculture systems. Resistant biotypes showed up in more weed species, more regions and in more crops. Therefore, every method or tool to control weeds, that potentially increases the selection pressure on herbicides and weeds must be handled with care. On the other hand new tools like herbicide tolerant varieties offer new possibilities for weed control. Particularly in sugarbeet, chemical weed control is still a compromise between efficacy and crop selectivity today. ALS-tolerant varieties offer the opportunity to improve crop safety and efficacy. To investigate the influence of these sugar beet varieties on the dynamic of ALS-resistant weed populations in a three-year crop rotation, a six-year field trial was conducted on two experimental sites. Four different weed control strategies were tested, which exhibit different levels of selection pressure to ALS inhibitors. The field trial showed that continuous use of ALS herbicides quickly increased the density of resistant weed populations leading to a large yield reduction. However, this process was much slower, when the frequency of ALS inhibitor use was reduced. Yet, it was not stopped completely. Even the use of alternative modes action was only partly able to slow down the resistance evolution. While weeds resistant to ALS herbicides only could be well controlled, multiple resistant weeds were able to build up a new resistance mechanism (ACCase inhibitor resistance). Here this was the case for Alopecurus myosuroides. As a consequence, use of alternative MoAs failed to control A. myosuroides. Due to these complex interactions sustainable use of herbicide tolerant varieties is not easy in the long run. Advantages might be long lasting when site-specific resistant weed status is adequately addressed.
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