A Toxicity Study of some plant Extracts Synergized with Sesame Oil against the Spiny Boll Worm Earias insulana

Abstract

This study was carried out in the laboratory of Entomology, Plant Protection Department , College of Agricultural Studies , Sudan University of Science and Technology (SUST) to evaluate the lethal effect of hexane extracts of the leaves of Rehan (Ocimum basilicum) and Lupine seeds (Lupinus termis) against the 3rd larval instars of spiny bollworm (Earias insulana Boisduval, 1833). Also further experiments were conducted to investigate the efficacy of sesame oil as a synergist. Four concentrations of hexane extracts of each plant were prepared and used in this study. The results showed that all tested concentrations of the two plant extracts gave higher significantly mortality percentage than the control. The lowest concentration (1.25%) of hexane extract of Rehan leaves gave only (36.7) mortality after 24 hrs of exposure; however, when mixed with sesame oil it increased to (60%).The synergized hexane extract of Rehan leaves at (5% and 10%) concentrations generated (93.3%) and (96.7%) mortality respectively after 24 hrs of exposure and the results were not significantly different from the standard insecticide, Engeo. On the other hand, the lowest concentration (1.25%) of hexane extract of lupine seeds gave only (20%) mortality after 24 hrs of exposure but when mixed with sesame oil it increased to (50%) mortality. After 72 hrs of exposure the highest concentrations of hexane extract of lupine seeds (10%) gave only (63.3%) whereas the same concentration of synergized hexane extract of Rehan leaves generated (100%) mortality after 72 hrs. The results obtained after 72 hrs of application showed that the LC50 values were (1.51 and 3.91) for Rehan and lupine respectively, but when sesame oil was admistrated the LC50 values was reduced to (0,75 and 1.06) for Rehan leaves and Lupine seeds respectively.