Ovarian development and ovipositional preference of the western corn rootworm (Coleoptera: chrysomelidae) variant in East Central Illinois

The rotation of maize, Zea mays L., and soybean, Glycine max (L.) Merr., has been the traditional cultural tactic to manage the western corn rootworm, Diabrotica virgifera virgifera LeConte, in the Corn Belt. The reduced effectiveness of this rotation as a pest management tool in east central Illinois, northern Indiana, and southern Michigan can be explained by the shift in the ovipositional behavior of the new variant of western corn rootwonn. The objective of this study was to evaluate the influence of maize, soy bean, oat, Avena sativa L., stubble, and alfalfa, Medicago sativa L., on the ovarian development and ovipositional preferences of the variant western corn rootworm. Field research was conducted near Urbana, IL, during 1998-2000. Gravid females were present throughout the season ill all crops, and due to the prolonged period in which western corn rootworin females can lay, eggs, none of the crops were immune from oviposition. Results indicated that the western corn rootworm variant oviposits ill maize, soybean, oat stubble, and alfalfa. In 1998 and 1999,, maize was the preferred oviposition site among crops; however, in 2000, maize, soybean, and oat stubble treatments had similar densities of western corn rootworm eggs. Lack of oviposition preference of the western corn rootworin variant demonstrated in this experiment represents a reasonable explanation of why the effectiveness of the rotation strategy to control western corn rootworm has diminished.