Abstract

Biological control potential of Beauveria bassiana and Paecilomyces species against Culex quinquefasciatus was investigated. The two fungi have been reported to exhibit insecticidal activity against mosquito and other insects. Beauveria bassiana and Paecilomyces spp was isolated from soil using soil suspension method with selective isolation media procedures. Bioassay was made to determine their efficacy against 4th instar larvae of C. quinquefasciatus. Three different concentrations; 1x107, 1x106 and 1x105 conidia/ml were made and tested. Results showed that mortality increased with increase in conidia concentration and exposure time. The mortality recorded in lowest dose of 105 conidia/ml was 70% and 50% in Beauveria bassiana and Paecilomyces spp respectively, and again 80% and 60% mortality were recorded at dose of 106 conidia/ml. The highest dose level of 107 conidia/ml of Beauveria bassiana and Paecilomyces spp isolate caused high mortality up to 90% and 80% respectively. 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 Beauveria bassiana isolate after 24-, 48-, 72- and 96-Hours exposure time were 3.9 ×108, 2.6 x 106, 2.0 x 104 and 1.6x106 conidia/ml. Similarly, LC50 values Paecilomyces spp isolate after 24,46,72,96-Hours exposure were 6.3×108, 4.8 x 107, 3.0 x 104 and 2.3 x 106 conidia/ml respectively. These results indicated that B. bassiana and Paecilomyces spp isolated is pathogenic to immature stage of C. quinquefasciatus and although not as efficient as chemical larvicides and could be suggested for development as a biological control for mosquito management so as to avoid concerns associated with chemical larvicides