Structural characterization of nanoparticles loaded with garlic essential oil and their insecticidal activity against Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae).

The aim of this work was to characterize polyethylene glycol (PEG) coated nanoparticles loaded with garlic essential oil and to evaluate their insecticidal activity against adult Tribolium castaneum . Preparation of nanoparticles was carried out using the melt-dispersion method, a very simple, convenient, and low-cost technique. The oil-loading efficiency could reach 80% at the optimal ratio of essential oil to PEG (10%). The morphology results and nanoparticle size showed that the nanoparticles had a round appearance and good dispersion, <240 nm in the average diameter, characterized by transmission electron microscope and dynamic light scattering, respectively. The abundance and percentage content of the major components did not show any significant difference between free and nanoencapsulated oil when analyzed by gas chromatography-mass spectrometry. The control efficacy against adult T. castaneum remained over 80% after five months, presumably due to the slow and persistent release of the active components from the nanoparticles. In contrast, the control efficacy of free garlic essential oil at the similar concentration (640 mg/kg) was only 11%. This indicates that it is feasible to use the PEG coating nanoparticles loaded with garlic essential oil to control the store-product pests.