Evaluation of the Insecticidal Activity of Nerium oleander L. against the Red Flour Beetle, Tribolium castaneum (Herbst) (Tenebrionidae, Coleoptera)

Abstract

Background: The red flour beetle, Tribolium castaneum (Herbst) (Tenebrionidae, Coleoptera) is a pest of worldwide distribution and can cause destructive damage to stored grains. The physicochemical properties and varied effects against insect pests make plant extracts a potential alternative in the development of pesticides. Methods: In this study, we assayed the oleander leaf extract toxicity effects against T. castaneum adults in the laboratory. We used four concentrations of Oleander methanol leaf extract. Result: Exposure of T. castaneum adult to the oleander leaf extracts produced 100% mortality in the insecticidal bioassay, especially at 40% concentration. The mortality % ranged from 13.3-100% after 48hrs. The mortality percentage of the red flour beetle adults decreased by increasing exposure periods. The mortality % was highly negatively correlated with exposure times (R= -0.97, P =.0001; R= -0.80 and P=.0001) at 40 and 20% concentrations, respectively. The overall results of the current study suggest that the leaf extract of Nerium oleander may possess potential insecticidal properties, which could potentially be employed in pest management. The infrared analysis of the oleander leaf extract showed many bioactive components associated with plant secondary metabolites; some of these identified phytochemical compounds have biological activity. Further, the phenol and flavonoid total were estimated. We conclude that the oleander leaf extract has the potential to be useful in managing stored grain insect pests, particularly T. castaneum, but that it must be handled and applied with extreme caution.