Distribution and Abundance of Corn Rootworm Species as Influenced by Topography and Crop Rotation in Eastern Nebraska

Over the past 30 yr the western corn rootworm (WCR) Diabrotica virgifera</it> LeConte, largely displaced the northern corn rootworm (NCR), D. longicornis</it> (Say), as the dominant rootworm species in eastern Nebraska. Only in the northeast cropping district has the NCR exhibited significant persistency. Here a comparative study of the ecology and behavior of the 2 species disclosed specific distributional and behavioral differences. The avg no. and percentage of the 2 species varied according to whether the samples were from “upland” or “lowland” fields. The NCR was significantly more abundant in upland fields. The NCR dispersed more readily from cornfields to weedy oat stubble and soybean fields, whereas the WCR for the most part moved from corn to other cornfields. These behavioral differences, coupled with prevailing farming practices (continuous corn vs corn in short rotations), partially explain the displacement phenomenon and varying degrees of coexistence now observed between the NCR and WCR in different areas of Nebraska. The southern corn rootworm (SCR), D. undecimpunctata howardi</it> Barber is of minor importance as a pest of corn in Nebraska.