Is the Biology of Corn Rootworms Changing in Iowa?

In east central Illinois during the summer of 1995, corn planted where soybeans had been grown the previous season was seriously damaged by the western corn rootworm (Diabrotica virgifera virgifera). Since then a variant of the western corn rootworm (often referred to as the eastern variant of the western corn rootworm ) that infests corn grown in rotation has spread throughout the northern half of Illinois, western Indiana, and southern Wisconsin and Michigan. The larvae of the variant are able to attack rotated corn because the adults no longer maintain their fidelity to corn as the preferred crop for egg laying; they will oviposit in other crops including soybeans. When corn is planted following the rotational crop, the soil is infested with eggs and the larvae that emerge find corn roots to attack and develop on. In the areas where the variant is found, damage to rotated corn has been severe. The lodging and yield losses have resulted in a dramatic increase in the use of insecticides, and a corresponding increase in production costs in rotated corn where little insecticide was applied for corn rootworm control prior to 1995