Larvicidal Activity of Entomopathogenic Fungus, Paecilomyces Specie Against Fourth Instar Larvae of the Mosquito Culex quinquefasciatus (Culicidae: Diptera)

Abstract

The biological control potential of Paecilomyces spp. against Culex quinquefasciatus was evaluated. Paecilomyces spp. was isolated from soil using the soil suspension method with selective isolation media. Bioassay was made to determine its efficacy against 4th instar larvae of Culex quinquefasciatus. Three different concentrations; 1x106, 1x107 and 1x108 conidia/ml were made and tested. Results showed that, mortality increased as the period of exposure increased and also increased as the conidia concentration increased. The mortality recorded in lowest dose of 106 conidia/ml was 50%, and again 70% mortality was recorded at dose of 107 conidia/ml. Whereas highest dose level of 108 conidia/ml caused high mortality of up to 80%. The lethal concentration causing 50% mortality (LC50) of 4th instars larvae of C. quinquefasciatus was also varied according to concentration of spores and duration of exposure. The result showed that LC50 values of Paecilomyces spp. isolate were 5.3×108, 3.8 x 107, 2.0 x 106 and 2.3 x 107 conidia/ml after 24, 48, 72 and 96 Hours exposure respectively. These results indicated that Paecilomyces spp. isolated was pathogenic to immature stage of C.quinquefasciatus and could be suggested for development as a biological control for mosquitos’ management.