Evaluation of larvicidal activities of Parthenium hysterophorus L. against Anopheles arabiensis (Diptera: Culicidae), the major malaria vector in Ethiopia

Malaria is a leading public health problem in Ethiopia despite the implementation of effective indoor vector control strategies over several decades. In the country, the use of botanicals to prevent the transmission of malaria is limited. This study aimed to evaluate the larvicidal activities of the extracts of the roots, stems, and leaves of Parthenium hysterophorus against the 4th instar larvae of Anopheles arabiensis. Field collected leaves, stems and root parts of P. hysterophorus were dried and separately ground to powder and extracted in petroleum ether, hexane, acetone, and ethanol solvents. The extracts were concentrated, and stock solutions were subject to serial dilutions for use as test concentrations. Laboratory reared 4th instar larvae of An. arabiensis were used for the larvicidal bioassays. Probit analysis was used to determine LC₅₀ and LC₉₀ of the extracts. There were significant differences in percentage larval mortalities (P < 0.05) among different concentrations of the leaf, stem, and root solvent extracts, respectively. Petroleum ether extracts of P. hysterophorus root were the most effective in causing very high larval mortality at 360 ppm and 480 ppm (98.3%) when compared to other extract of the plant parts. The LC₅₀ and LC₉₀ value of petroleum ether root extract (10.7 ppm and 105.5 ppm respectively) were significantly lower than those of ethanol, acetone, and hexane root extracts. Petroleum ether root extract of P. hysterophorus has remarkably high larvicidal potential against 4th instar larvae of An. arabiensis which could be exploited for malaria vector control. Further studies on the larvicidal efficacy of the extracts under field conditions and identification of the bioactive components in the root parts of this plant are recommended.