In this study, the changes in the conventional nutrient and mineral compositions as well as the metabolomics characteristics of the red palm weevil (RPW) Rhynchophus ferrugineus Olivier (Curculionidae: Coleoptera) larvae at early (EL), middle (ML) and old (OL) developmental stages were investigated. Results showed that the EL and ML had the highest content of protein (53.87 g/100 g dw) and fat (67.95 g/100 g), respectively, and three kinds of RPW larvae were all found to be rich in unsaturated fatty acids (52.17–53.12%), potassium (5707.12–15,865.04 mg/kg) and phosphorus (2123.87–7728.31 mg/kg). In addition, their protein contained 17 amino acids with the largest proportion of glutamate. A total of 424 metabolites mainly including lipids and lipid-like molecules, organic acids and their derivatives, organic heterocycle compounds, alkaloids and their derivatives, etc. were identified in the RPW larvae. There was a significant enrichment in the ABC transport, citrate cycle (TCA cycle), aminoacyl-tRNA biosynthesis, and mTOR signaling pathways as the larvae grow according to the analysis results of the metabolic pathways of differential metabolites. The water extract of EL exhibited relatively higher hydroxyl, 2,2-diphenyl-1-pyrroline hydrochloride (DPPH) and 2,2’-azobis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical-scavenging ability with the EC₅₀ values of 1.12 mg/mL, 11.23 mg/mL, and 2.52 mg/mL, respectively. These results contribute to a better understanding of the compositional changes of the RPW larvae during its life cycle and provide a theoretical grounding for its deep processing and high-value utilization.

Insect-specific pathogens present a sustainable alternative to pesticides for managing the red palm weevil (RPW). This study assessed the efficacy of Steinernema carpocapsae ALL nematodes and their symbiotic bacteria against the third-instar larvae and adults of RPW under laboratory conditions. The symbiotic bacteria were isolated, morphologically characterized, and genetically identified. The results indicated that the mortality rates of RPW larvae treated with S. carpocapsae exceeded 50% in all treatments at 120 h, reaching 93.33% at a concentration of 250 IJs/mL. The morphology of isolated symbiotic bacterium from S. carpocapsae on NBTA medium exhibited a light green color with a glossy surface, a raised center, and a mucilaginous texture. A novel strain of symbiotic bacterium was identified and named as LZ-G7. The bacteria toxicity on RPW adults showed a notable mortality rate of 66.67% at 48 h after feeding with concentration of 10 × 10⁷ CFU/mL. The mortality rate of the third-instar larvae of RPW reached 83.33% after feeding with 0.30 × 10⁸ CFU/g at 96 h and 93.33% after injection into blood cavity with 8 × 10⁶ CFU at 48 h. These results suggest that S. carpocapsae and a novel symbiotic bacterium strain exhibit strong virulence against RPW and have the potential to serve as effective biological control agents in integrated pest management strategies.