Insecticide activity of the essencial oil Tanaecium nocturnum (Barb. Rodr.) Bur. & K. Shum (Bignoneaceae) on Sitophilus zeamais Motsch. (Coleoptera: Curculionidae)

Abstract

Insecticidal activities of Tanaecium nocturnum (Barb. Rodr.) Bur. & K. Shum (Bignoneaceae) essential oil against Sitophilus zeamais Motsch. (Coleoptera: Curculionidae). The essential oil extracted from fresh leaves of the Tanaecium nocturnum (Barb. Rodr.) Bur. & K. Shum by steam distillation, was tested against maize weevil Sitophilus zeamais Motsch.. Filter paper and maize grains impregnation was employed, for contact and fumigant toxicity effect studies, respectively. For topical effect studies, aliquots of 0,5 μl of the diluted oil applied to adults insects. We used a broad range of concentrations to be used for establish the most promising concentrations. Probit analysis was employed in analyzing the dose/ concentration-mortality response (LD 50 and LC50). Linear regression analysis was applied in mortality of maize weevil adults. The toxicity (LC50) T. nocturnum oil to S. zeamais was of 14.1 ng.cm-2 and LC50 of 1,321.6 ng.g-1 of the grains for contact and fumigant effects, respectively, and LD50 of 14.7 μg.mg-1 of the insect for topical application. For contact and fumigant effects, the mortality rate was nearly 100% at oil concentrations of 2 % and 5% (m/v), and 4% and 5% (m/v), respectively. For contact, fumigant, and topical effects, the mortality rate was nearly 100% at oil concentrations of 2 % and 5% (m/v); 4% and 5% (m/v) and 10% (m/v) respectively. The current study shows that cyanidric acid, liberated from the essential oil of the T. nocturnum, posses fumigant insecticidal effect on S. zeamais in concentrations more than 4% (m/v) were promises.