Insecticidal effects of the powdery formulation based on clay and essential oil from the leaves of Clausena anisata (Willd.) J. D. Hook ex. Benth. (Rutaceae) against Acanthoscelides obtectus (Say) (Coleoptera: Bruchidae)

The bioefficacies of essential oil and aromatized clay powder based on the mixture of clay and essential oil extracted from Clausena anisata were evaluated for their insecticidal activities and their effects on progeny production of Acanthoscelides obtectus. Contact toxicity assayed by coating on bean grains showed that these chemicals caused significant mortality of the test insect. Beetle mortality was dose dependant and after 2-day exposure the aromatized clay powder was more toxic (LD₅₀ = 0.069 μl/g grain) than the pure essential oil (LD₅₀ = 0.081 μl/g grain). There was, however, a highly significant loss of toxicity after 24 and 36 h following treatment with essential oil and aromatized powder, respectively. Both aromatized clay powder and pure essential oil considerably reduced the F₁ progeny insect production. The essential oil evoked moderated repellent action and high fumigant toxicity (LC₅₀ = 0.093 μl/cm³) against adults of A. obtectus. These results suggest that the clay powder could be used to stabilize the essential oil to increase its efficacy for use as an alternative to synthetic insecticides.