Construction of star polycation-enabled delivery system for pymetrozine nanometerization: Enhanced aphid control and excellent ecological safety

Abstract

The long-term irrational use of conventional chemical pesticides places considerable pressure on agroecosystems. As an emerging tool, nanotechnology shows great promise for enhancing pesticide activity and utilization efficiency. In this study, the star polycation (SPc) and pymetrozine (PYM) combine to form a novel nanopesticide (PYM@SPc) via hydrogen bond-driven self-assembly, whose physicochemical properties and bioactivity are systematically evaluated. The results show that PYM@SPc forms a rod-like nanoparticle (approximately 424 ​nm). The PYM@SPc significantly reduces the droplet contact angle, improves spreading and adhesion on both leaf surfaces and pest cuticles, and greatly enhances plant uptake (1.38-fold). Bioassays demonstrate that the PYM@SPc markedly enhances both stomach toxicity (26.67 ​%) and integrated toxicity (36.67 ​%) against green peach aphids (Myzus persicae), while field trials further confirm its superior control efficacy (91.19 ​%) compared with free PYM (61.19 ​%). Ecotoxicological assessment reveals that even at high concentrations, the formulation does not negatively affect the hatching or emergence rates of natural enemies (Harmonia axyridis, Arma chinensis and Trichogramma ostriniae). Taken together, this study presents a low-cost nano-delivery strategy that achieves high efficacy of PYM at low doses, while ensuring the ecological safety of non-target natural enemies.