Slow-release pesticide microparticles from polylactic acid and emamectin benzoate: preparation and characteristics

Emamectin benzoate (EMB) is a potent biological pesticide with broad-spectrum activity against various insects and fungi; however, its practical application is limited due to rapid degradation under UV irradiation, sunlight, and elevated temperatures. In this study, EMB was successfully encapsulated into polylactic acid (PLA) microparticles to enhance its stability, prolong its activity, and improve utilization efficiency. The effects of initial EMB content, PLA solution concentration, and particularly surfactant composition on the microparticle characteristics were systematically investigated. The optimized conditions yielded uniform microparticles with an average diameter of 3.24 μm, a loading content (LC) of 28.74%, and an encapsulation efficiency (EE) of 86.23%. The encapsulation markedly improved both UV and thermal stability of EMB, while in vitro release studies demonstrated a significantly sustained and controllable release profile compared with free EMB. These results suggest that PLA-based encapsulation provides an efficient delivery system for EMB, offering potential as a smart pesticide formulation to support sustainable agricultural practices.