Laboratory and field experiments were carried out to assess the interactions patterns between two biocontrol agents of the legume pod borer Maruca vitrata. With the importation of the parasitoid wasp Apanteles taragamae from Taiwan to Benin for a classical biological control against M. vitrata, it was important to evaluate its non target effects namely its interactions with other biocontrol agents in use such as the fungal entomopathogen Beauveria bassiana. In laboratory, a concentration of 109 conidia/ml of B. bassiana isolate Bb115 was applied to Maruca larvae prior to their submission to parasitization by A. taragamae. In other experiments, M. vitrata larvae were parasitized first by females of A. taragamae before the fungal suspension application. A lot of M. vitrata larvae were considered as control without parasitization and fungal suspension application. The number of dead larvae, A. taragamae cocoons, sporulated dead larvae were counted. In field trials, cowpea plants were sprayed with B. bassiana suspension at a dose of 75 g of spores powder. Then, 28 m2 cowpea plots were delimited and covered with net before the release of 5 A. taragamae mated females in each delimited cage. Results revealed that B. bassiana did not induce significant mortality in the parasitoid and might affect parasitic potential. The overall mortality rate averaged 52.07±0.9% in B. bassiana associated with A. taragamae treatments against 50.46±1.3% in control treatments. Moreover, additive effect was observed between the two biocontrol agents. Data were discussed with regard to the simultaneous use of the two biocontrol agents for controlling M. vitrata in cowpea.
