Toxicity and Physiological Effect of Lemongrass Essential Oil Nano-capsules on the Greater Wax Moth Larvae Galleria mellonella L. (Lepidoptera: Pyralidae)

The current study focuses on the insecticidal activity of a nanoencapsulated lemongrass essential oil (LEO) (Cymbopogon citratus) using chitosan as a natural polymer encapsulate, against the larvae of greater wax moth (Galleria mellonella) under laboratory conditions. The study also examines various biological and physiological changes. Gas chromatography-mass spectrometry (GC/MS) analysis of LEO revealed that citral is the primary compound, representing by 70.33% of the total essential oil composition followed by myrcene, geranyl acetate and cis-verbenol. Dynamic light scattering and scanning electron microscopy were used to characterize the preparation of the nanocapsules. Results indicated that treatment over three weeks had satisfactory effects on biological aspects including larval mortality, larval weight, and some morphological deformities. Specifically, 46.59% of the treated larvae were lost during their development to adulthood at the lowest concentration, while the larval loss was recorded at 92.05% at the highest concentration, with an LC50 of 49.89 ppm. The study demonstrated a significant reduction in larval weight and various malformations. Treated larvae exhibited a large increase in chitinase activity, while a significant suppression of the enzymatic activity of the protease, acetylcholinesterase, acid, and alkaline phosphatase was observed. These results suggest that LEO-nanocapsules cause biological and physiological disturbances in G. mellonella larvae and may be potentially integrated into pest management IPM programs.