Limited efficacy of florpyrauxifen‐benzyl alone for Lolium perenne L. spp. multiflorum and Poa annua L. control: The need for herbicide combinations in hazelnut (Corylus avellana L.) orchard management

Abstract

Hazelnut (Corylus avellana L.) production is an important agricultural industry in the Willamette Valley of OR, where growers face persistent challenges from weed and sucker management. This study investigates the efficacy of florpyrauxifen‐benzyl to control weeds and suckers in hazelnut orchards and optimise hazelnut production. Florpyrauxifen‐benzyl had no adverse effects on tree health, growth or yield when applied up to 117.6 g ai ha⁻¹ four times per year for two consecutive years. Florpyrauxifen‐benzyl controlled hazelnut suckers, achieving >83% control 84 days after initial treatment. In greenhouse studies, florpyrauxifen‐benzyl suppressed Lolium multiflorum and Poa annua growth, although regrowth was observed. In field studies, florpyrauxifen‐benzyl did not control L. multiflorum, but it effectively suppressed inflorescence biomass by 88%. When florpyrauxifen‐benzyl was combined with glyphosate, clethodim, rimsulfuron, diuron, tiafenacil or glufosinate, it did not negatively impact L. multiflorum control compared to individual herbicides. For instance, at an application rate of 29.4 g ai ha⁻¹, florpyrauxifen‐benzyl reduced L. multiflorum inflorescence biomass by 98%–99% when combined with glyphosate compared to 97%–99% with glyphosate alone. Colby's test confirmed the additive effects of florpyrauxifen mixtures, indicating that these herbicides can broaden the control spectrum and improve management practices. This study highlights the potential for using florpyrauxifen‐benzyl in combination with other herbicides to develop a more integrated weed and sucker management approach in hazelnuts. The adoption of herbicide rotation and the use of multiple modes of action are essential for reducing the risk of resistance and ensuring long‐term orchard management.