Aggregation Sites for Adult European Corn Borers (Lepidoptera: Crambidae): A Comparison of Prairie and Non-Native Vegetation

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Abstract
Moths of the European corn borer, Ostrinia nubilalis (Hübner), aggregate in vegetation during the day. We examined the preference of moths for different types of vegetation as aggregation sites and investigated several physical characteristics of vegetation that might determine moth preference. We focused primarily on vegetation types that occur along roadsides adjacent to cornfields. In the Midwest, roadside vegetation typically consists of brome grass, Bromus inermis (Leyss). We were especially interested in the moth’s preference for prairie vegetation compared with brome because several states have begun planting prairie vegetation along roadsides. At 4 central Iowa study sites, the density of moths was measured in several vegetation types during the 1st and 2nd O. nubilalis generations. For each vegetation type we also measured its microclimate and its foliage density at 5 vertical levels. In the 1st generation, moths were most dense in brome, which had 6.9 times more moths than prairie. In the 2nd generation, moths were most dense in foxtail grass, Setaria spp. Foxtail had 5.2 times more moths than brome, and brome had 1.6 times more moths than prairie. In both generations, the moth density in a vegetation type was significantly positively correlated with foliage density at 60 cm. Microclimate measurements of different vegetation types were not consistently correlated with moth density. We conclude that O. nubilalis moths prefer dense foliage >60 cm tall. We also conclude that replacing roadside brome and the weedy foxtail with native prairie has the potential to reduce the number of adult moths breeding near cornfields.