Efficacy of Solanum villosum Mill. (Solanaceae: Solanales ) as a Biocontrol Agent against Fourth Instar Larvae of Culex quinquefasciatus Say


Abstract: Dried ground leaves of Solanum villosum, Mill. were extracted with 5 different solvents [petroleum ether, benzene, choloform:methanol (1:1 v/v), acetone, and absolute alcohol] to determine the best extractant for subsequent isolation and characterization of larviciding compounds. Each batch of larvae (10 per batch) was treated with 30 ppm, 50 ppm, and 100 ppm of each extract in 3 replicates. All eluted fractions were found to induce significant mortality in test mosquito species. The petroleum ether eluted fraction was the least toxic, whereas the chloroform:methanol (1:1 v/v) eluted fraction was the most toxic to the larvae. A very high mortality rate (86.67%) was observed at 100 ppm test solution after 24 h of exposure. LC_{50} values of the leaves with biologically active different solvent extracts like petroleum ether, absolute alcohol, benzene, acetone, and chloroform:methanol (1:1 v/v) were 645.745 ppm, 321.890 ppm, 204.302 ppm, 107.657 ppm, and 39.192 ppm, respectively, after 24 h of exposure period. Mortality rate with chloroform:methanol (1:1 v/v) extract was significantly higher (P < 0.05) in 100 ppm than in other extracts. The bioactive fraction of chloroform:methanol (1:1 v/v) was isolated by thin layered chromatography (TLC), and the LC_{50} value was determined as 3.179 mg/100 ml after 24 h of study period.

Keywords: Solanum villosum, Culex quinquefasciatus, biocontrol, bioassay, LC_{50}

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