Susceptibility of four cereal and legume pests to Beauveria bassiana and Metarhizium anisopliae isolates

Abstract: Laboratory bioassays were performed to evaluate the efficacy of the commercial Beauveria bassiana strain ATCC74040 (Naturalis), and Metarhizium anisopliae CIST8 against adults of four grain and legume pest species, Cathartus quadricollis, Callosobruchus maculatus, Sitophilus granarius, and Oryzaephilus surinamensis. Three conidial suspension concentrations were used 103, 105, and 107 conidia/ml for all isolates. Five repetitions per isolate/concentration were carried out. In the Petri assay, 20 insects were sprayed with the conidial suspension mixed with tween 80 (0.002 %). Plates were then incubated in climatic cells at 26 °C. Mortality data was recorded daily and the final mortality rate was considered after 7 days. The results of our laboratory assays revealed significant differences in mortalities of insect species among EPF species. Differences were found among the selected insect species in their susceptibility to the two fungal isolates. The highest concentration (107 conidia/ml) of the M. anisopliae CIST8 and B. bassiana ATCC74044 isolates induced the highest mortality rates against C. maculatus (85 % and 97 %, respectively). Metarhizium anisopliae CIST8 isolate showed the lowest efficacy against O. surinamensis (25-30 %). Our results suggest that EPF could be effective as part of an integrated pest management program for the control of legumes and grain pests.