Efficacy of different entomopathogenic fungi against cowpea aphid, Aphis craccivora (Koch).

Laboratory bioassay studies were carried with six different concentrations of Beauveria bassiana (Bals.) Vuill., Metarhizium anisopliae (Metsch.) Sorokin., Verticillium lecanii (Zimm.) Viegas., Hirsutella thompsonii (Fisher) and Cladosporium oxysporum (Berk. and Curt.) against the adults of Aphis craccivora. In the high concentration (10 8 spores ml -1 ) 100% mortality was obtained with V. lecanii and H. thompsonii followed by B. bassiana, M. anisopliae and C. oxysporum. Mortality declined with the decrease in concentrations. The lowest LC 50 value of 2.5x10 4 spores ml -1 was recorded by V. lecanii and H. thompsonii isolates, which showed higher virulence compared to other isolates. The LC 50 values of B. bassiana, M. anisopliae and C. oxysporum were 4.5x10 4 , 8.9x10 5 and 7.4x10 5 spores ml -1 respectively. At the highest concentration of 10 8 spores ml -1 , the Median LT 50 values for B. bassiana, H. thompsonii, V. lecanii, C. oxysporum and M. anisopliae were 3.63, 3.64, 3.90, 5.24 and 5.54 days, respectively. The LT 50 values were found to be inversely proportional to the spore concentrations. Among the five entomopathogenic fungi, V. lecanii, H. thompsonii and B. bassiana were found to be the promising virulent isolates. By testing their field efficacy, they can be used as potential biocontrol agent for the management of cowpea aphid.