Pathogenicity of Metabolites of Nematophagous Fungus Paecilomyces Lilacinus Against the Larvae of Anopheles Stephensi And Culex Quinquefasciatus

Abstract

Mohammed R. Annon Al- hasnawi

The main aim of the present investigation was to elucidate the pathogenic effect of secondary metabolites nematophagous fungus Paecilomyces lilacinus (Order: Monilialis) against all larval instars of malaria vectors, Anopheles stephensi and filaria vectors, Culex quinquefasciatus. However, the efficacy of these metabolites has so far not been tested as mosquito larvicide and this is the first report on it. P. lilacinus was previously isolated from adult housefly cadaver and grown on PDA medium, thereafter was cultured on PDB at 25 1 C° and 70 5% R.H for fifteen days, the extracellular metabolites were filtered by using whatman no.1 filter paper. The efficacies were conducted at five different concentrations (25, 50, 75, 100 and 150) ppm. and the mortalities of all larval instars for both mosquito vectors were assessed after 24, 48 and 72 hrs. and LC50 values were determined by probit analysis. The results showed that mortality percentages of all tested instar were directly proportional for both metabolites concentration, exposure time and inversely to larval age. Early instars of An. stephensi and Cx. quinquefasciatus were highly vulnerable to metabolites and mortality exceeded 90% after 72 hrs., therefor the metabolites of P. lilacinus were found better equipped against early instars for both species. The LC50 values were 24.5, 28.72, 32.78 and 40.96 ppm. for the four larval instars of An. stephensi respectively while in case of Cx. quinquefasciatus these values were 37.65, 42.88, 47.36 and 53.10 ppm. after 72 hrs. Overall, the results of susceptibility had shown the degree of tolerance to metabolite was in order 1st > 2nd > 3rd >4th instar, and the metabolites induced high mortalities in all instars of An. stephensi comparable to Cx. quinquefasciatus. Eventually, the larvicidal potential of P. lilacinus metabolites may be altributed to secretion of bioinsecticidal molecules, like paecilotoxins and dipliconic acid, these can be fast acting metabolites for controlling larvae of malaria and filaria vectors.