Chitosan‐grafted polylactic acid as a novel pesticide carrier: optimizing etoxazole release, boosting mite control, and minimizing environmental impact

Abstract BACKGROUND Conventional acaricides face challenges of environmental persistence and non‐target toxicity. To address this, a chitosan‐grafted polylactic acid ( CS ‐co‐ PLA ) controlled‐release system was rationally designed as a biodegradable carrier for etoxazole (Eto), aiming to enhance acaricidal efficacy while minimizing ecological risks. This study focuses on synthesizing Eto@ CS ‐co‐ PLA through ring‐opening polymerization and evaluating its controlled‐release behavior, bioactivity against Tetranychus urticae and environmental biosafety. RESULTS The hexahedron‐shaped Eto@ CS ‐co‐ PLA exhibited a uniform particle size (3.45 ± 0.77 μm, scanning electron microscopy ) with 9.05% drug loading. The release followed first‐order kinetics ( R 2 = 0.986), with the CS ‐co‐ PLA carrier showing slowed release in later stages. At 72 h, cumulative release reached 83.65% for R‐etoxazole and 82.44% for S‐etoxazole. Bioassays revealed superior ovicidal activity (median lethal concentration = 0.170 mg L −1 ), 1.5‐fold lower than free Eto (0.259 mg L −1 ; P < 0.001), but no acute toxicity to adult mites or earthworms. Enhanced leaf adhesion (contact angle: 45 ± 2.2° versus 63.4 ± 2.5° for Eto) and adhesion work ensured reduced environmental loss. Biosafety assessments demonstrated crop growth promotion and non‐target safety. CONCLUSION The Eto@ CS ‐co‐ PLA controlled‐release system demonstrated excellent slow‐release capabilities, achieving high efficacy against T. urticae without acute toxicity to adult mites and earthworms. Its biodegradability and plant growth‐promoting properties ensured minimal environmental impact. This study provides a sustainable paradigm for precision application of agricultural chemicals, achieving a balance between insecticidal efficiency and ecological safety. © 2025 Society of Chemical Industry.