Evaluation on Biocontrol Efficacy of <i>Episyrphus balteatus</i> De Geer (Diptera: Syrphidae) Against <i>Aphis craccivora</i>, <i>Myzus persicae,</i> and <i>Megoura crassicauda</i>.

Abstract

Larvae of <i>Episyrphus balteatus</i> De Geer (Diptera: Syrphidae) are important natural enemies of common agricultural pests such as aphids (Hemiptera: Aphididae). This well-known aphidophagous flower fly is used as a biological control agent. The predatory functional responses, control efficacy, and oviposition and predatory preferences of <i>E. balteatus</i> against <i>Aphis craccivora</i> Koch, <i>Myzus persicae</i> Sulzer, and <i>Megoura crassicauda</i> Mordvilko were systematically determined through controlled laboratory experiments. The best functional response model of both second- and third-instar <i>E. balteatus</i> larvae to these three aphid species was the Holling type III model, except for the third-instar larvae to <i>A. craccivora</i>, for which the Holling type II model was superior. The <i>A. craccivora</i> population decline rates for ratios of 1:500 and 1:1000 were 94.67% and 100.00% on day 12 after inoculation; the <i>M. persicae</i> population decline rates for ratios of 1:2000 and 1:4000 reached 96.67% and 95.42% by day 12, and the <i>M. crassicauda</i> population at a ratio of 1:250 was completely eliminated by day 9, achieving a 100.00% population decline rate. The oviposition and predatory preferences of <i>E. balteatus</i> were consistent, in that it preferred <i>M. crassicauda</i> for oviposition and had a positive predatory preference for this aphid species. These results provide scientific evidence for the biological control strategy of <i>E. balteatus</i> against these aphids.