Preparation of nontoxic nano-pesticides with safe nanocarrier: First synergistic application with parasitoid enemy for shorter initial acting time and longer control persistence toward insect pests

The dual challenges of long initial acting time of natural enemies and short control persistence of pesticides underscore the urgent need to co-apply selective pesticides and natural enemies for synergistic pest management. Herein, we developed two nano-pesticides that are nontoxic to parasitoid wasps using the safe nanocarrier hydrophilic-lipophilic diblock polymer (HLDP), and their synergistic application with parasitoid wasps effectively shortened the initial acting time and prolonged the control persistence, achieving high population suppression against common cutworms. The biosafety of two polymeric nanocarriers HLDP and cationic star polymer (SPc) was evaluated toward parasitoid wasp Meteorus pulchricornis via contact and oral exposure, recording eclosion rate and adult survival. Both nanocarriers were relatively safe via contact exposure but induced dose-dependent oral toxicity at high concentrations (HLDP LC 50 = 5.643 mg/mL; SPc LC 50 = 2.860 mg/mL), with HLDP exhibiting superior biocompatibility. Oral feeding of HLDP at an extremely high concentration down-regulated various genes associated with metabolism and membrane, damaged the intestinal ultrastructure, and led to systemic metabolic dysfunction and gut microbiota dysbiosis in parasitoid wasps, suggesting membrane damage-mediated metabolic impairment as the primary lethal mechanism. Subsequently, using HLDP as a nanocarrier, we formulated nano‑pesticides with abamectin (AVM) and chlorantraniliprole (CTP), reducing their particle sizes to 105 nm and 215 nm and increasing zeta potentials to + 50.84 mV and + 47.57 mV, respectively. Remarkably, two nano-pesticides displayed stronger stomach and contact toxicity against common cutworms compared to AVM/CTP alone by approximately 20–30%. Notably, the parasitoid wasps were insensitive to nano-pesticides with unaffected eclosion rate (100%), and displayed strong parasitic selectivity toward alive larvae of common cutworms. The co-application of two nano-pesticides with parasitoid wasps achieved > 82% population suppression of common cutworms in the simulated environment, effectively overcoming the long initial acting time of parasitoid wasps and short control persistence of nano-pesticides. Our study provides an excellent precedent for synergistic co-application of nano-pesticides with parasitoid enemies.