Seasonal Abundance of Resident Parasitoids and Predatory Flies and Corresponding Soybean Aphid Densities, with Comments on Classical Biological Control of Soybean Aphid in the Midwest

Abstract

Seasonal abundance of resident parasitoids and predatory flies, and corresponding soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), densities were assessed in soybean fields from 2003 to 2006 at two locations in lower Michigan. Six parasitoid and nine predatory fly species were detected in 4 yr by using potted plants infested with soybean aphid placed in soybean fields. The parasitoid Lysiphlebus testaceipes Cresson (Hymenoptera: Braconidae) and the predatory flies Aphidoletes aphidimyza Rondani (Diptera: Cecidomyiidae), and Allograpta obliqua Say (Diptera: Syrphidae) were most numerous. Generally, L. testaceipes was more abundant late in the soybean growing season, but it also occurred during soybean vegetative growth; A. obliqua was more abundant during vegetative growth; and A. aphidimyza was common throughout the season. Soybean plants were visually inspected to estimate densities of soybean aphid, mummified aphids, and immature predatory flies. From 2003 to 2006, parasitism rates were inversely correlated with aphid density: percentage of parasitism was always very low (< or = 0.1%) at high aphid densities (> 100 aphids per plant), and higher parasitism, up to 17%, was observed at very low aphid densities (< 1 aphid per plant). Populations of immature predatory flies, particularly A. aphidimyza, generally increased in soybean fields with increasing soybean aphid populations, but aphids always outnumbered immature flies by 100-21,000-fold when flies were detected. Rearing field-collected aphid in 2006 substantiated that parasitism varied widely, with parasitism in most cases < 10%. Based on findings of low parasitism and predation, positive response to changing aphid densities by predatory flies but not parasitoids, early season abundance primarily of predatory flies, and past findings on these taxa's diversity and abundance, we discuss the potential use of exotic parasitoids and predatory flies to enhance soybean aphid biological control.

Life table and predation rates of the syrphid fly Allograpta exotica, a control agent of the cowpea aphid Aphis craccivora

“…A. obliqua is also a well-known aphidophagous flower fly with potential as BCA (Smith and Chaney, 2007;Noma and Brewer, 2008;Hopper et al, 2011) but immature stages of both Allograpta species are not yet distinguishable using morphology (Arcaya, 2012).…”

European buckthorn and Asian soybean aphid as components of an extensive invasional meltdown in North America

“…In China and the Eastern United States, both generalist predators and more specialized parasitoids are important (van den Berg et al 1997;Liu et al 2004;Wu et al 2004b;Miao et al 2007;Nielsen and Hajek 2005;Hajek et al 2007;Wu, Heimpel and Hopper, unpublished data;see below). In the NorthCentral US, however, parasitoids have little impact on A. glycines (Lin and Ives 2003;Rutledge et al 2004;Costamagna and Landis 2006;Kaiser et al 2007;Noma and Brewer 2008;Noma et al 2010) and at least one predator that is present in Eastern N. America (A. muelleri) is absent from soybean fields (see below). In Asia, parasitism rates ranging between 45 and 52% were routinely recorded over a 5 year period in Jilin province (Gao 1994), one of the principal soybean producing areas.…”

“…A number of both native and introduced predators, parasitoids and pathogens have been documented consuming the soybean aphid since its introduction in North America in 2000 (e.g. Rutledge et al 2004;Nielsen and Hajek 2005;Mignault et al 2006;Kaiser et al 2007;Chacon et al 2008;Noma and Brewer 2008) and the presence of soybean aphid could lead to enrichment of any of these species. Such enrichment could lead to a number of indirect ecological effects, chief among these being apparent competition, where an increase in abundance of a consumer of one species leads to increased consumption of one or more different species (Holt and Lawton 1994).…”

Compatibility of aphid resistance in soybean and biological control by the parasitoid Aphidius colemani (Hymenoptera: Braconidae)

“…While parasitoids appear to have a more prominent role in controlling soybean aphid populations in eastern Asia (Liu et al, 2004;Wu et al, 2004;Miao et al, 2007), several native and previously established parasitoids have been found to attack soybean aphids in North America (Kaiser et al, 2007;Noma and Brewer, 2008).…”

“…A. colemani was introduced in the early 1990s to control the Russian wheat aphid in North America and has subsequently become established at several locations. A. colemani has been shown to attack soybean aphid in the field (Lin and Ives, 2003;Kaiser et al, 2007;Noma and Brewer, 2008). In part because of its preference for attacking larger aphids and its ability to control soybean aphid population growth rates (Lin and Ives, 2003;Chacón et al, 2008), A. colemani has been considered as a potential biological control agent of the soybean aphid.…”