Potential of Beauveria bassiana for the Control of Maize Weevil and Bean Beetle in the Laboratory

Abstract

The susceptibility of the maize weevil, Sitophilus zeamais Motsch., and the bean beetle, Callsobruchus chinensis L., to ten isolates of Beauveria bassiana (Balsamo) Vuillemin was studied in the laboratory. Adult insects were exposed to spore suspensions of B. bassiana isolates at a concentration of 1X108 conidia ml'1. Controls were sprayed with 0.01 % Tween 80 in distilled water. All isolates tested were capable of infecting both test insects but their virulence, determined by adult mortalities and median lethal time (MLT), varied. A total of five (189-481, 190-520, 189-477,190-533 and 190-907) most virulent (MLT = 2.8-4.2 days), three (192-736, 193-906, and I92-761A) intermediate (MLT = 4.2-6.03 days) and two (193-868 and 193-870) weakly (MLT >7.5 days) virulent isolates were identified against 5. zeamais. On the other hand, based on four days cumulative mortality data, five (190- 520, 190-533, 192-736,194-907 and 189-477) virulent (MLT = 1.9-2.4 days); three (189-481, 192-761A and 193-906) intermediate (MLT = 1.3-2.5 days) and two (193- 870 and 193-868) weakly virulent (MLT = 3.1-3.5 days) isolates were identified on C. chinensis. The study considered B. bassiana as a potentially valuable mycopathogen for the microbial control of storage pests.