Larvicidal and Synergic Effects of two Biopesticides (Azadirachta indica and Metarhizium anisopliae) against Larvae of Culex quinquefasciatus (Diptera, Culicidae) (Say, 1823)

Abstract

Mosquitoes in general and Culex quinquefasciatus in particular have for a long time constituted a source of nuisance due to the diseases they transmit, stings and annoying buzzing. They are also a public health problem. This is why this study is aimed at finding a biopesticide that can fight effectively but also be an alternative to chemical residual pesticides in the environment. Concentrations of biopesticides used are ranged from 2.5 108 to 12.5 108 spores/ml with intervals of 2.5 108 spores/ml for Metarhizium anisopliae. Concentrations ranging beetween 8 10-4g/ml to 40 10-4 g/ml with intervals of 8 10-4 g/ml of Azadirachta indica (Suneem 1%) were used to fight against 100 three instars larvae of Culex quinquefasciatus. Concentrations of the mixture of Azadirachta indica (Sunnem 1%) and Metharhium anisopliae ranging from 0.02 ml +2 108 spores/ml to 0.02 ml + 1 108 spores/ml were used to study synergic effects of these two biopesticides. One hundred (100) of three instars larvae of Culex quinquefasciatus are used as control and placed in the same jars with 500 ml of distilled water. Metarhizium anisopliae (green muscle) have caused 50% mortality of three instars larvae of Culex quinquefasciatus after 3 days. Azadirachia indica (Suneem 1%) have gaved a mortality more than 60% after 2 days. The mixture Azadirachta indica (Suneem1%) and Metarhizuim anisopliae caused a high mortality with a rate that exceeds 90% in 3 days. The mixture also prevented a larval moult thus stopping their growth and development. In summary, both Metharizium anisopliae and Azadirachta indica (Suneem 1%) are effective against three instars larvae of Culex quinquefasciatus. Their mixture caused a synergic effect and thus increased their individual efficacy of two biopesticides.