Evaluation of the Insecticidal Activity of Cinnamomum verum Bark Extract against the Red Flour Beetle, Tribolium castaneum (Coleoptera: Tenebrionidae)

Abstract

This study was conducted to assess the insecticidal potential of Cinnamomum verum Presl bark extract against the red flour beetle, Tribolium castaneum (Herbst), a major cosmopolitan pest of stored grain products. Bark powder was macerated in hydroethanolic solvent, concentrated, and freeze-dried, and the extract was characterized using Fourier transform infrared (FT-IR) spectroscopy to identify major functional groups and associated phytochemical classes. The FT-IR analysis revealed at least 18 biologically active functional groups. Contact toxicity was assessed with a residual film (treated filter paper) bioassay, in which adult beetles were exposed to graded concentrations of the extract (6.13–50%) for 12–48 h under controlled laboratory conditions. Bioassay results indicated that adult mortality increased significantly with both extract concentration and exposure time, with no mortality in the control. At 48 h, mortality reached about 69.7% at the 50% concentration, whereas the lowest concentration caused only minimal mortality. Morphological and histopathological observations, supported by light and scanning electron microscopy, revealed paralysis, cuticular darkening and shrinkage, and structural damage in treated beetles compared with intact, turgid controls, suggesting disruption of cuticle integrity and vital physiological functions. Overall, the findings indicate that C. verum bark extract has strong dose- and time-dependent contact toxicity against T. castaneum adults and may represent a promising botanical candidate for integration into ecofriendly, residue-reduced stored-product pest management strategies.