A 4‐year field study monitoring the evolution of Trp574Leu‐resistant plants in an Echinochloa crus‐galli population under different crop rotation and herbicide programs in maize.

BACKGROUND: A 4‐year experiment evaluated the effects of different integrated weed management (IWM) programs on the evolution of a Echinochloa crus‐galli population resistant to acetolactate synthase (ALS) inhibitors in a maize cropping system. The programs included the continued use of ALS inhibitors, mixing them with alternative herbicides, or without ALS‐inhibitors, in all cases under maize monocrop or a biennial crop rotation. RESULTS: IWM programs that relied solely on non‐ALS‐inhibitors usually achieved high control levels across years (> 90%). Additionally, Trp574Leu‐resistant plants became prevalent (> 90%) in programs only using ALS inhibitors, while in the rest the frequency of susceptible plants did not substantially decrease below 40%. Regarding the other monitored grass weeds, Digitaria sanguinalis and Panicum dichotomiflorum were effectively controlled in programs using ALS‐inhibitors without soybean rotation or in programs without ALS‐inhibitors altogether, excepting the program relying on an 4‐hydroxyphenylpyruvate dioxygenase (HPPD)‐inhibitor under maize monocrop for the latter species (0%). CONCLUSION: At the end of the experiment, the only IWM programs that reduced infestation levels were the one without ALS‐inhibitors under soybean rotation, and the one with standard pre‐emergence treatments. These findings highlight the effectiveness of crop rotation and alternative herbicides both pre‐ or post‐emergence in controlling E. crus‐galli. ALS‐inhibitors, while challenged by resistance in E. crus‐galli, remain valuable tools for managing other grass weed species in maize. It is crucial to adapt IWM strategies for herbicide‐resistant E. crus‐galli and other grass weed populations to mitigate the further evolution of resistance. © 2024 Corteva Agriscience. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. [ABSTRACT FROM AUTHOR]