Biological control potential of Metarhizium anisopliae against Culex quinquefasciatus was evaluated. M. anisopliae was isolated from soil using soil suspension method with selective isolation media. Bioassay was made to determine its efficacy against 4th instar larvae of C. quinquefasciatus. Three different concentrations; 1 × 106, 1 × 107 and 1 × 108 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 60%, and again 80% mortality was recorded at dose of 107 conidia/ml. whereas highest dose level of 108 conidia/ml caused high mortality of up to 90%. 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 M. anisopliae isolate were 3.8 × 108, 2.5 × 106, 2.0 × 105 and 1.7 × 107 conidia/ml after 24, 48, 72 and 96 Hours exposure respectively. These results indicated that M. anisopliae isolated is pathogenic to immature stage of C. quinquefasciatu and could be suggested for development as a biological control for mosquitos’ management
