Carbon Quantum Dot Nanoparticles Enhance the Efficacy of Spodoptera littoralis Nucleopolyhedrovirus Suspoemulsion

This study evaluates the efficacy of Spodoptera littoralis nucleopolyhedrovirus (SpliNPV) and laboratory-synthesized carbon quantum dot nanoparticles (CQDNPs) against the second instar Spodoptera littoralis larvae under laboratory and greenhouse conditions. Individually, both SpliNPV and CQDNPs exhibited substantial lethality (91.6% and 83.3% at 1 × 10⁸ OBs/ml and 700 mg/ml, respectively) (p < 0.05). The LC₅₀ values were 1.88 × 10⁵ OB/ml and 434.2 mg/mL, and the LT₅₀ values were 8.9 and 9.8 days, respectively. Four LC-based combined treatments demonstrated significant additive effects, with the SpliNPV (LC₅₀) + CQDNPs (LC₂₅) combination achieving the optimum effect with a mortality rate of 86.3% and an LT₅₀ value of 6.6 days, leading to its selection for the suspoemulsion nanoparticle (SENP) formulation. The SENP formulation displayed superior performance, achieving the highest mortality rates and fastest killing times across all environments: 89.0% in laboratory conditions, 83.3% on eggplant plants, and 76.6% on pepper plants. In contrast, the suspoemulsion (SE) and unformulated (UF) formulations showed lower efficacy, emphasizing the importance of formulation in enhancing the biological activity of SpliNPV. The LT₅₀ values further supported these findings, with the SENP formulation demonstrating the shortest LT₅₀ values, indicating faster lethality. A significant decrease in CHS-B, IIM2, PER3, REPAT14, and CDA1 expression was observed, particularly in the combined CQDNPs + SpliNPV treatment, while API expression increased significantly. These findings highlight the potential of nanoparticle-enhanced formulations like SENP, and integrating CQDNPs with SpliNPV can significantly enhance pest control efficacy.