Spray droplet size and carrier volume effect on dicamba and glufosinate efficacy

BACKGROUND Pesticide applications using a specific droplet size and carrier volume could maximize herbicide efficacy while mitigating particle drift in a precise and efficient manner. The objectives of this study were to investigate the influence of spray droplet size and carrier volume on dicamba and glufosinate efficacy, and to determine the plausibility of droplet‐size based site‐specific weed management strategies. RESULTS Generally, across herbicides and carrier volumes, as droplet size increased, weed control decreased. Increased carrier volume (187 L ha−1) buffered this droplet size effect, thus greater droplet sizes could be used to mitigate drift potential while maintaining sufficient levels of weed control. To mitigate drift potential and achieve satisfactory weed control (≥ 90% of maximum observed control), a 900 µm (Ultra Coarse) droplet size paired with 187 L ha−1 carrier volume is recommended for dicamba applications and a 605 µm (Extremely Coarse) droplet size across carrier volumes is recommended for glufosinate applications. Although general droplet size recommendations were created, optimum droplet sizes for weed control varied significantly across site‐years. CONCLUSION Convoluted interactions occur between droplet size, carrier volume, and other application parameters. Recommendations for optimizing herbicide applications based on droplet size should be based on a site‐specific management approach to better account for these interactions. © 2018 Society of Chemical Industry Herbicide applications using a specific droplet size and carrier volume emitted from a pulse‐width modulation sprayer were evaluated for dicamba and glufosinate efficacy across broad geographies to create application optimization recommendations.