Abstract:
This study was conducted at the laboratory of Entomology, Plant Protection Directorate, Kosti Station, to evaluate the effect of hexane and ethanol organic extracts of Sakran, Datura innoxia, Usher, Calotropis procera leaves and Malathion 57% EC on mortality of the African bollworm Helicoverpa armigera. Four concentrations (4%,8%,12%and 16%) of each extract were prepared and tested against the second larval instar. The results showed that all tested concentrations gave significantly higher mortality percentages than that of the control. The LC50 values of the ethanolic extract of Usher leaves after 24, 48 and 72 hrs of exposure were 20.5, 13.1 and 7.9 respectively, whereas those of hexane extracts were 14.3, 6.7 and 5.169 respectively. The LC50 of the ethanolic extract of Sakran leaves after 24, 48 and 72 hrs of exposure were 14.1, 6.7 and 3.7 respectively whereas those of the hexane extract of Sakran leaves were 7.3, 4.7 and 2.2 respectively. These results clearly show that both ethanolic and hexane extracts of sakran leaves were more activity than their counterparts of usher leaves.
The results also show that the LC50 obtained by hexane extract of Sakran leaves after 24, 48 and 72 hrs of exposure were consistently lower than their counterparts of Sakran leaves ethanolic extract. This may indicate that the active ingredient in Sakran leaves is easily extracted in hexane rather than in ethanol. The mortality results generated by the 16% concentration of hexane and ethanol extract of Sakran leaves were not significantly different from that of the standard, malathion, after 24, 48 and 72 hrs of exposure which is an indicative of the high potency of these extracts.
