Insecticidal Activity of Polyethylene Glycol Nanocapsules of Clove Essential Oil against Sitophilus oryzae and Tribolium castaneum

Abstract

The present study was aimed to prepare clove oil nanocapsules (PEG-ClO NCs) and to investigate their insecticidal potential against stored grain pests including Sitophilus oryzae and Tribolium castaneum. Nanocapsules were synthesized by the melt dispersion method. The 10% PEG-ClO NCs formed the most stable nanocapsules with 270.30 nm size, 0.25 PDI, and 90.03% encapsulation efficiency. Scanning electron microscopy images showed slightly irregularly shaped nanocapsules in a good dispersion. The major phytochemicals identified in GC-MS analyses of pure clove oil were eugenol, phenol, and caryophyllene. Contact toxicity bioassay revealed that clove essential oil nanocapsules showed 100% mortality against Tribolium castaneum and Sitophilus oryzae after 3 and 7 days of exposure, respectively. The LC50 values for nanocapsules were 2260.89 and 10498 mg/kg against S. oryzae and T. castaneum. The residual contact toxicity of pure oil was reduced gradually and after 4 weeks it showed 61.67 % and 58.36 % mortality upon exposure as compared to PEG-ClO NCs that showed 95.67 % and 93.33% mortality against Sitophilus oryzae and Tribolium castaneum respectively. The results of this study suggested that PEG-based nanocapsules prevented the clove essential oil evaporation and rapid degradation while allowing a persistent and slow release. It is concluded that PEG nanocapsules loaded with clove essential oil are feasible to be used as bioinsecticide against stored grain pests for a long time.