1. Division of Science, Truman State University, Kirksville, MO 63501.
2. Corresponding author: Phone: 660-785-4280. Fax: 660-785-7604. E-mail: campbell@truman.edu
3. USDA-ARS Corn Insect and Crop Genetics Research Unit, Agronomy Dept, Iowa State University, Ames, IA
4. Agronomy Department, Purdue University, West Lafayette, IN 47907