Polymeric nanoparticles containing different oils as insecticides against the storage pest Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae)

Garlic oil (GO) and cinnamon oil (CO) was successfully loaded in chitosan (CS) based polymeric nanoparticles (NPs). Fumigant, contact toxicities and persistent efficacy of these new Chitosan nano particles (CSNPs) were examined against Tribolium castaneum (T. castaneum) as a common stored product pest. Different ratios of polymer to sodium tripolyphosphate cross-linker were applied for NPs preparation. Stability of CSNPs loaded with oils was examined for 4 months. Bioassay tests were used to determine LC50 values for fumigant toxicity evaluation and contact effects on red flour beetle, T. castaneum. The optimized CSNPs containing GO and CO had the particle size of 231.1 +/- 7.5 nm and 303.4 +/- 10 nm with encapsulation efficiency of 76.78% and 86.81%, respectively. Characterization results based on transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) indicated the successful formation of CSNPs with spherical morphology, amorphous property, and high stability during the storage time. LC50 index of pure oils and their nanoformulations suggested that CSNPs loaded oils have higher fumigant and contact effects on T. castaneum in a lower concentration than pure oils. Lethal effectiveness of CSNPs loaded GO and CO against T. castaneum were 18 and 20 days, respectively. However, GO and CO pure oils lost their efficacy in 10 and 14 days after exposure, respectively.

Automated summary

Garlic oil and cinnamon oil were successfully loaded into chitosan-based polymeric nanoparticles. These nanoparticles showed higher fumigant and contact toxicities against Tribolium castaneum compared to pure oils. The nanoparticles also exhibited a longer persistent efficacy against the pest.