Comparative Evaluation of Repellent and Toxicant effects of some selected botanicals Bio-oils against the Red Flour Beetle, Tribolium castaneum Herbst (Coleoptera: Tenebrionidae)

The Red Flour Beetle, Tribolium castaneum Herbst (Coleoptera: Tenebrionidae), is a significant pest of stored grain products, leading to substantial economic losses globally due to its ability to infest a variety of food products, including wheat, flour, and cereals. Traditionally, chemical insecticides have been employed to control these pests; however, their prolonged use has led to concerns about the development of resistance, environmental toxicity, and adverse effects on non-target organisms. Consequently, there has been an increasing interest in exploring botanical alternatives, particularly essential oils, which are derived from plants and are known for their insecticidal, repellent, and growth-regulating properties. This study investigates the repellent and toxic effects of four widely used botanical bio-oils—neem oil (Azadirachta indica), eucalyptus oil (Eucalyptus globulus), clove oil (Syzygium aromaticum), and citronella oil (Cymbopogon citratus)—against T. castaneum. The repellent efficacy was evaluated using a two-choice arena test, and the toxic effects were assessed through a contact bioassay, with concentrations ranging from 0.5% to 4% for each oil. The results showed that neem oil exhibited the highest repellent and insecticidal activity, followed by clove oil, citronella oil, and eucalyptus oil. Neem oil’s high efficacy can be attributed to its active compound, azadirachtin, known for its repellent and toxic properties. Clove oil, containing eugenol, also demonstrated significant repellent and insecticidal effects. Citronella oil displayed moderate efficacy, while eucalyptus oil was the least effective among the oils tested. These findings suggest that botanical bio-oils, particularly neem and clove oils, have the potential to serve as effective, eco-friendly alternatives to chemical insecticides in managing stored-product pests, providing a more sustainable approach to pest control in grain storage systems. Further studies are warranted to explore the optimal application techniques and synergistic effects of combining these oils for enhanced pest management in real-world scenarios.