Larval development and voracity of Eupeodes americanus (Diptera: Syrphidae): comparison of the focal prey Aphis gossypi (Hemiptera: Aphididae) and the banker prey Rhopalosiphum padi (Hemiptera: Aphididae)

Unlike European species,the potential of Nearctic syrphids as biological control agents is still poorly studied.However,the American hoverfly,Eupeodes americanus(Wiedemann),has recently demonstrated promising traits as a biocontrol agent,notably against the foxglove aphid,Aulacorthum solani Kaltenbach,on pepper.The present study aims to extend our knowledge of the American hoverfly by evaluating its potential as a biocontrol agent in a banker plant system against the melon aphid,Aphis gossypi Glover,in a greenhouse cucumber crop.The preimaginal development and voracity of E.americanus were compared when preying upon the focal prey/pest(A.gossypi)or the banker prey(bird cherry-oat aphid,Rhopalosiphum padi L.)by daily observations of larvae from egg to adult.Preimaginal development time,survival rate,and occurrence of deformation were similar on both prey species.The weight of third instar and pupae,however,was higher for larvae that fed on the banker prey.The ad libitum voracity of the syrphid larvae was generally very high and did not significantly differ between prey species,except for the third-instar larvae which consumed more focal prey.Results suggest that a banker plant system involving the bird cherry-oat aphid may be a promising tactic for utilizing E.americanus for melon aphid biocontrol.