Dendritic Mesoporous Silica Nanoparticle-Based Co-Delivery of a Repellent and an Insecticide for Management of the Asian Citrus Psyllid

The Asian citrus psyllid (Diaphorina citri) serves as the principal insect vector responsible for the transmission of citrus Huanglongbing (HLB). Consequently, the effective control of D. citri is of paramount importance for curbing the spread of this devastating disease. Fir essential oil (FEO) exhibits a potent repellent activity against D. citri; however, its practical application is severely constrained by a short duration of efficacy arising from its high volatility. Imidacloprid (Im) is a conventional insecticide widely used for D. citri management, and prolonging its residual activity remains a critical challenge for field application. In this study, we synthesized dendritic mesoporous silica nanoparticles (DMSNs, ≈257 nm) and employed them to construct a nano-pesticide formulation co-loaded with both Im and FEO. Our results demonstrated that DMSNs possessed high loading capacities for Im (21.79%) and FEO (32.98%). Notably, both Im and FEO within the DMSNs-Im-FEO formulation exhibited favorable sustained-release profiles and significantly extended residual activities compared to their free counterparts. Furthermore, the DMSNs-Im-FEO formulation displayed preliminary non-target tolerance in citrus plants, Chinese milk vetch, and earthworms, indicating its low ecotoxicological risk. Overall, our study provides a novel and promising strategy for the sustainable management of D. citri, which holds considerable significance for the integrated management of HLB.