Optimization of the formulation of cyhalofop-butyl spreading oil by response surface methodology and its field efficacy

To address the limitations of traditional spray formulations for rice field herbicides-namely, low labor efficiency and high environmental contamination risk-this study employed the Box-Behnken response surface design to optimize the formulation of cyhalofop-butyl spreading oil. The film-forming adjuvant dodecanol ester (C-12), surfactant 601, and Triton X-100 were selected as key independent variables, with diffusion area and diffusion speed as response variables. A quadratic regression model was constructed and subjected to analysis of variance (ANOVA) to identify the optimal formulation. The fitting of the diffusion area and diffusion speed model for 9% cyhalofop-butyl spreading oil were highly significant (p < 0.0001), with non-significant lack-of-fit values, indicating strong model fitness and predictive capability. The coefficients of determination (R²) for diffusion area and diffusion speed were 0.9942 and 0.9869, respectively. All three factors exhibited significant nonlinear effects on the responses, and the interaction between C-12 and Triton X-100 significantly influenced both diffusion area and speed (p < 0.05). Through multi-response optimization, the optimal formulation was determined as follows: C-12 4.0%, surfactant 601 3.2%, Triton X-100 2.2%, with No. 150 solvent oil making up to 100%. Based on this formulation, five cyhalofop-butyl spreading oil products with active ingredient contents of 9%, 8%, 7%, 6%, and 5% were prepared. Quality index evaluation and indoor bioactivity assays indicated that the 6% formulation exhibited the best overall performance. Subsequently, the 6% formulation was selected for field efficacy trials, at a dose of 2100 g/hm² achieving a 14-day control efficacy of 91.86% against Echinochloa crus-galli (L.) P. Beauv., demonstrating excellent herbicidal activity. This study provides a theoretical foundation and technical support for the formulation optimization of cyhalofop-butyl spreading oil and offers a promising labor-saving strategy for weed management in paddy fields.