Oviposition Preference of the American Hoverfly, Eupeodes americanus, between Banker Plants and Target Crops

Simple Summary Oviposition preference of aphidophagous hoverflies is a key factor in the biological control of aphids, especially when using banker plant systems. In this laboratory study, the oviposition preferences of Eupeodes americanus were evaluated in two-choice experiments with different plant/aphid systems. The results show that the finger millet banker plant may be more suitable for the control of A. gossypii in cucumber crops and the barley banker plant for the control of M. persicae in pepper crops. Finally, this study demonstrates that the oviposition of E. americanus can be adequate for the control of aphids in a mixed crop of cucumber and pepper. Future semifield or field studies are needed to confirm these recommendations. Assessing the oviposition preferences of predatory hoverflies is a key factor in the prediction of the success of these biological control agents against aphids in greenhouses, especially when using banker plant systems or in mixed-crop contexts. In this study, two aspects of the oviposition preferences of the American hoverfly, Eupeodes americanus (Wiedemann, 1830) (Diptera: Syrphidae), were evaluated. Firstly, the preference between the banker plant and the target crop was evaluated for three banker plant species (barley, finger millet, or corn) and two target crops (cucumber or pepper). Secondly, the preference between the same two target crops was assessed. Female oviposition preferences were evaluated via two-choice experiments using different plant/aphid systems. The results showed that, for the cucumber crops, the species of banker plant used drastically influenced the oviposition preference of the hoverfly, with a preference for barley over cucumber, cucumber over finger millet, and no preference between corn and cucumber. Unlike cucumber, when used with pepper, barley engendered a preference for the target crop. We conclude that the barley banker plant could be adequate for aphid control in pepper but not in cucumber crops. In a mixed-crop context, the American hoverfly had no preference between cucumber and pepper, which means it has the potential to protect both crops in a mixed-crop greenhouse context. This study shows that the banker plant system should be carefully chosen according to the crops/aphids present in the greenhouse to optimize the impact of the hoverfly as a biocontrol agent. Further work is required to confirm this choice of banker plant in semifield or field testing.