Aggregation sites for adult European corn borers (Lepidoptera : Crambidae): A comparison of prairie and non-native vegetation

Moths of the European corn borer, Ostrinia nubilalis (Hubner), aggregate in vegetation during the day. We examined the preference of moths for differe nt types of vegetation as aggregation sites and investigated several physic al characteristics of vegetation that might determine moth preference. We f ocused primarily on vegetation types that occur along roadsides adjacent to cornfields. In the Midwest. roadside vegetation typically consists of brom e grass, Bromus inermis (Leyss). We were especially interested in the moth' s preference for prairie vegetation compared with brome because several sta tes have begun planting prairie vegetation along roadsides. At 4 central Io wa study sites, the density of moths was measured in several vegetation typ es during the Ist and 2nd O. nubilalis generations. For each vegetation typ e we also measured its microclimate and its foliage density at 5 vertical l evels. In the Ist generation, moths were most dense in brome, which had 6.9 times more moths than prairie. In the 2nd generation, moths were most dens e in foxtail grass, Setaria spp. Foxtail had 5.2 times more moths than brom e, and brome had 1.6 times more moths than prairie. In both generations, th e moth density in a vegetation type was significantly positively correlated with foliage density at 60 cm. Microclimate measurements of different vege tation types were not consistently correlated with moth density. We conclud e that O, nubilalis moths prefer dense foliage >60 cm tall. We also conclud e that replacing roadside brome and the weedy foxtail with native prairie h as the potential to reduce the number of adult moths breeding near cornfiel ds.