Insecticidal Efficacy and Chemical Composition of Hexane Oil Extracts from the Leaves of Euphorbia milii and Cassia occidentalis

Abstract

Insecticidal efficacy of oils from the leaves of Cassia occidentalis and Euphorbia milii on selected insect pests was studied. The oils were extracted via Soxhlet apparatus with hexane, and test insects exposed to the oils at 3 dose levels (0.2 mg, 0.4 mg and 0.6 mg) for 24 hours. The results showed contact insecticidal activity of E. milii oil at LD50s and LD90s (mg/kg) as 0.583 and 1.108 for Periplaneta americana, 0.681 and 1.215 for Tettigonia viridissima 0.488 and 0.893 for Anopheles gambaie, C. occidentalis oil gave LD50s and LD90s (mg/kg) of 0.889 and 1.689 for P. americana, 1.013 and 1.973 for T. virdissima, and 0.722 and 1.847 for Anopheles gambaie. The corresponding values for the conventional insecticide; SWAN were 0.417 and 1.017 for P. americana, 0.607 and 1.111 for T. viridissima and 0.40 and 0.743 for A. gambaie, respectively. The GC-MS analysis of plant oils revealed for E.milii, the presence of hexadecanoic acid, 2 hydroxy-1-(hydroxymethyl) ethyl ester; 6, 9,12, 15-docosatetraenic acid methyl ester. For C. occidentalis, the presence of: phthalic acid isobutyl octyl ester; hexadecanoic acid methyl ester;  9,12-octadecadienoic acid methyl ester ; 9-octadecenoic acid (z)-methyl ester; methyl stearate; phthalic acid,2-ethylhexyl isohexyl ester; decane; oleic acid; 4,7,-methano-1h-indene,3a,4,7,7a-tetrahydro and n-hexadecanoic acid were revealed. Overall, data from this study provides strong evidence that these oils possess bioactive metabolites with commendable degrees of insecticidal efficacy.