The Effect of Some Plant Extracts on Mortality of the African bollworm Helicoverpa armigera (Hübner),(Lepidoptera:Noctuidae)

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.

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