Application of Acetochlor Nanocapsule Formulation in Sichuan Ophiopogon japonicus Fields

Weeds pose a significant threat to the production of the medicinal crop Ophiopogon japonicus. Due to the scarcity of registered herbicides for this crop, farmers heavily rely on manual weeding. This study evaluated a novel acetochlor nanocapsule formulation for weed control in Sichuan O. japonicus fields, comparing it to a conventional acetochlor emulsifiable concentrate (EC). Treatments included manual weeding (weed-free control), conventional EC (900 g a.i. ha−1), and three nanocapsule doses (450, 900, and 1800 g a.i. ha−1). Weed control efficacy was assessed at 15, 30, 45, and 60 days after application, followed by the measurement of agronomic traits, yield, and the content of bioactive compounds (saponins, flavonoids, and polysaccharides) post-harvest. The high-dose nanocapsules (1800 g a.i. ha−1) provided excellent weed control (96.54% at 45 days), which was better than the EC and lower nanocapsule doses, and extended the control duration. It did not negatively affect key agronomic traits, root tuber morphology, final yield, nor the content of key bioactive compounds compared to the weed-free control. In conclusion, acetochlor nanocapsules, especially at 1800 g a.i. ha−1, offer an effective and safe weed management strategy for O. japonicus. They provide superior, prolonged weed control without harming crop yield or quality.