Evaluation on Biocontrol Efficacy of De Geer (Diptera: Syrphidae) Against , and .

Larvae of 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 against Koch, Sulzer, and Mordvilko were systematically determined through controlled laboratory experiments. The best functional response model of both second- and third-instar larvae to these three aphid species was the Holling type III model, except for the third-instar larvae to , for which the Holling type II model was superior. The population decline rates for ratios of 1:500 and 1:1000 were 94.67% and 100.00% on day 12 after inoculation; the population decline rates for ratios of 1:2000 and 1:4000 reached 96.67% and 95.42% by day 12, and the 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 were consistent, in that it preferred for oviposition and had a positive predatory preference for this aphid species. These results provide scientific evidence for the biological control strategy of against these aphids.