Eco-friendly pH-responsive iron-doped insect larval frass extract as a hexaconazole nano-delivery system for controlling fungal disease and promoting crop growth

Developing environmentally friendly pesticides and improving pesticide utilization efficiency are urgent needs for modern agriculture. Herein, a pH-responsive biodegradable dual pesticide-fertilizer was fabricated using extracts from naturally occurring Protaetia brevitarsis larval frass (PBLF) material. Iron ions (Fe3+) were integrated as metal nodes into PBLF, and hexaconazole (Hex), a triazole fungicide, was encapsulated in Fe-PBLF with a loading rate of 22.93 %. Hex@Fe-PBLF nanoparticles (NPs) presented a sphere-like construction with a hydrated size of 715.3 ± 5.0 nm and exhibited acid-responsive controlled release behavior, gradually self-degrading in acidic environments within 120 h. The NPs showed good foliar adhesion and were effectively absorbed and translocated by pathogenic fungal mycelium and the rice seedling. Compared with Hex Technical control (TC), the control effects of Hex@Fe-PBLF against Rhizoctonia solani (R. solani) and Botrytis cinerea (B. cinerea) increased by 9.9 % and 12.73 %, respectively, after 7 days. This naturally sourced nanocarrier not only promoted the growth of rice seedlings as a fertilizer but also enhanced their stress resistance. The low mobility of Hex@Fe-PBLF NPs in soil effectively reduced environmental risks. The excellent biosafety of the Fe-PBLF nanocarrier was further evaluated. Overall, this environmental-friendly multifunctional nano pesticide-fertilizer has promising application potential in agriculture.