The larger grain borer (LGB), Prostephanus truncatus (Horn) is a cosmopolitan and major storage pest of maize causing up to 48% dry weight loss. Chemical pesticides are available for the management of this pest but these have potential negative effects on the consumer and the environment if misused. Thus, the present study aimed at assessing the compatibility of two bio-control agents (Teretrius nigrescens and Beauveria bassiana isolate IMI389521) for management of this pest. Two doses (1 × 109 CFU/Kg maize and 1 × 1010 CFU/Kg/maize) of B. bassiana, with and without the predator, T. nigrescens, were applied to maize containing P. truncatus. Controls with no B. bassiana were also tested. The results showed that the control had the lowest grain weight (P<0.05) whereas maize protected with upper dose (1 × 1010 CFU/Kg maize) of B. bassiana product only had the highest grain weight. Similarly, P. truncatus mortality was lowest (P<0.05) in the control and highest in the maize treated with the upper dose of the B. bassiana product followed by maize treated with the lower dose (1 × 109 CFU/Kg maize) of the B. bassiana product. Also, the B. bassiana product killed T. nigrescens but its mortality was less than fourfold that of P. truncatus in maize treated with the upper dose of B. bassiana product. In maize treated with the lower dose of B. bassiana product, T. nigrescens mortality was less than eightfold that of P. truncatus. Thus, the lower dose of the B. bassiana product can be used in storage systems where T. nigrescens is already established.
Key words: Beauveria bassiana, Teretrius nigrescens, LGB, maize, storage, bio-control.
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