Submitted to: Experimental and Applied Acarology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/21/2011
Publication Date: 10/11/2011
Citation: Prischmann-Voldseth, D.A., Knutson, E.M., Dashiell, K.E., Lundgren, J.G. 2011. Generalist-feeding subterranean mites as potential biological control agents of immature corn rootworms. Experimental and Applied Acarology. 55:233-248. Interpretive Summary: Predatory mites are commonly found in agro-ecosystems, and are help to reduce crop pests. Western corn rootworms are a severe pest of corn throughout North America, and their larvae are fed on by many predators. Here, we describe the mite community in corn fields, as it relates to corn rootworm immatures. A diverse community coincides with corn rootworm eggs and larvae, and we found that many of these species would consume rootworm immatures in the laboratory to varying degrees. This work suggests that mites are an important source of mortality for corn rootworms that merit more attention in the future.
Technical Abstract: Predatory mites are important components of subterranean food webs and may help regulate densities of agricultural pests, including western corn rootworms (Chrysomelidae: Diabrotica virgifera virgifera). Implementing conservation and/or classical biocontrol tactics could enhance densities of specialist or generalist predatory mites and lead to pest suppression, but first relevant mite species must be identified and their predatory capabilities evaluated. We conducted a survey of indigenous soil mites (non-Cryptostigmata) within a continuous corn environment. A diverse assemblage of mites was recovered that was dominated by generalist predators (e.g. Laelapidae). With the exception of Pseudolaelaps, densities of the most abundant predatory mesostigmatid taxa were negatively correlated with densities of first instar corn rootworm. However, correlations were generally weak, and only significant for Digamasellidae and Alloparasitus species. We then conducted no-choice lab assays to determine if mites recovered from maize fields and commercially-available soil-dwelling mites would consume immature corn rootworms and calculated daily consumption and oviposition rates. All mites tested [Geolaelaps aculeifer, Stratiolaelaps miles, Macrocheles insignitus, Glyptholaspis americana, Hypoaspis sp. (nr. dubia), Eviphis sp.] fed upon corn rootworm immatures and consumed more first instars than eggs. Glyptholaspis americana had the highest rate of predation (1.6 larvae and 0.6 eggs per day), followed by S. miles, although the latter had a higher oviposition rate. The degree of predation by the primarily nematophagous Eviphis species was extremely low, but indicated that feeding rates in experimental arenas may be slightly elevated. Although none of the mites tested appeared to specialize on corn rootworms, all species fed on this prey to some degree. It appears that the community of generalist soil-dwelling mites may play an important role in regulating immature corn rootworm populations in the field.