Technical Abstract: The European corn borer, Ostrinia nubilalis (Hübner), is a serious pest of commercial maize throughout the U.S. Corn Belt. Adults aggregate in grassy areas around and within the cornfield where they spend the daylight hours resting, and where mating activity occurs at night. Mated females leave the aggregation sites at night to oviposit in cornfields, thus using the grass as a staging area. Flush samples were taken in borrow ditches in central Iowa during the first (spring) flight of moths in 2003 and 2004 to determine if cropping patterns and crop phenology influence moth distribution across the landscape. Significantly more moths were present in ditches with an adjacent cornfield on at least one side of the road than in those with no corn on either side. In contrast, effects of corn stubble from the previous year's crop, tillage, and corn phenology were weak or not detectable. Evidence suggests that some moths emerging from corn stubble may aggregate in adjacent grass, but that they redistribute themselves in the landscape within a short time. Thus, the presence or absence of adjacent corn was the overwhelming factor affecting spatial distribution of first-flight European corn borer moths among grassy ditches.