A nano-delivery system expands the insecticidal target of thiamethoxam to include a devastating pest, the fall armyworm

Trypsin-encoding gene function of efficient star polycation nanomaterial-mediated dsRNA feeding delivery system of Grapholita molesta

BACKGROUND

Grapholita molesta is an important and harmful fruit pest worldwide, with widespread feeding hosts. Trypsin, an indispensable hydrolytic digestive protease in the insect gut, is crucial in digestion, growth and development. We analyzed the characteristics of the trypsin-encoding genes, screened for the optimal dose of RNAi mediated by nanocarriers, and investigated various indices of larval growth and development of G. molesta.

RESULTS

Gut content (GC) and RNase A degraded double-stranded RNA (dsRNA), with a faster degradation rate at higher concentrations. Star polycation (SPc) nanomaterials protected dsGFP from degradation by anion-cation binding and did not migrate through agarose gel. The key conserved motifs of the trypsin-encoding genes were similar, exhibiting high homology with those in other lepidopteran insects. An interference efficiency of ≈70% was achieved with SPc nanomaterial-mediated RNA interference with 0.05 μg dsRNA. The efficiency of continuous interference was stable. Trypsin activity, body weight of 8-day-old larvae, pupal weight and emergence rate were significantly reduced, and the larval stage was significantly prolonged.

CONCLUSION

The investigated trypsin gene is a key target gene in the growth and development of G. molesta. We investigated the efficiency and convenience of feeding SPc nanomaterials in a functional study of insects. Our results provide valuable data for the development of efficient trypsin-targeting pesticides. © 2024 Society of Chemical Industry.

Perfect cooperative pest control via nano-pesticide and natural predator: High predation selectivity and negligible toxicity toward predatory stinkbug

The improper use of synthetic pesticides has caused adverse effects on global ecosystems and human health. As a part of sustainable pest management strategy, natural predators, along with nano-pesticides, have made significant contributions to ecological agriculture. The cooperative application of both approaches may overcome their limitations, substantially reducing pesticide application while controlling insect pests efficiently. Herein, the current study introduced a cationic star polymer (SPc) to prepare two types of nano-pesticides, which were co-applied with predatory stinkbugs Picromerus lewisi to achieve perfect cooperative pest control. The SPc exhibited nearly no toxicity against predatory stinkbugs at the working concentration, but it led to the death of predatory stinkbugs at extremely high concentration with the lethal concentration 50 (LC50) value of 13.57 mg/mL through oral feeding method. RNA-seq analysis revealed that the oral feeding of SPc could induce obvious stress responses, leading to stronger phagocytosis, exocytosis, and energy synthesis to ultimately result in the death of predatory stinkbugs. Then, the broflanilide and chlorobenzuron were employed to prepare the self-assembled nano-pesticides via hydrogen bond and Van der Waals force, and the complexation with SPc broke the self-aggregated structures of pesticides and reduced their particle sizes down to nanoscale. The bioactivities of prepared nano-pesticides were significantly improved toward common cutworm Spodoptera litura with the corrected mortality increase by approximately 30%. Importantly, predatory stinkbugs exhibited a strong predation selectivity for alive common cutworms to reduce the exposure risk of nano-pesticides, and the nano-pesticides showed negligible toxicity against predators. Thus, the nano-pesticides and predatory stinkbugs could be applied simultaneously for efficient and sustainable pest management. The current study provides an excellent precedent for perfect cooperative pest control via nano-pesticide and natural predator.

Star Polymer-Based Nanodelivery System for Pesticides: Enhanced Broad-Spectrum Toxicity and Selective Toxicity

The application of nanotechnology in agriculture can break through many traditional problems of synthetic pesticides, especially for increasing bioactivity and reducing application amount. However, the safety and selective toxicity of nanocarrier-loaded pesticides should be clarified toward natural predators. In this context, an efficient spirotetramat nanodelivery system was successfully constructed based on a star polymer (SPc). Spirotetramat could complex with SPc through hydrogen bonding and van der Waals forces spontaneously. The self-assembly of the spirotetramat/SPc complex decreased the particle size of spirotetramat from 1292 to 710 nm. After the complexation with SPc, the lethal concentration 50 (LC50) values of spirotratemat decreased from 252.064 to 108.871 and 332.079 to 189.257 mg/L toward target pest Frankliniella occidentalis and nontarget predator Orius sauteri with the synergic ratios of 2.315 and 1.755, respectively. The possible reason might be due to the enhancement of the broad-spectrum toxicity of SPc-loaded pesticides. Importantly, the selective toxicity ratio (STR) of spirotetramat increased from 1.32 to 1.73 with the help of SPc, indicating the higher selectivity of the spirotratemat/SPc complex toward predators. Meanwhile, the safety coefficient (SC) of spirotratemat was not significantly changed after complexation with SPc, and the spirotratemat/SPc complex belonged to the medium risk pesticide. Overall, the assembly with SPc could not only improve the control efficacy of spirotetramat but also increase its selectivity as well as alleviate its negative effects on predators. The current study is beneficial for understanding the enhancement of broad-spectrum toxicity and the selective toxicity of nanocarrier-loaded pesticides.