Insecticide Resistance in the Adult Western Corn Rootworm in Nebraska1

Abstract

Adults of the western corn rootworm. Diabrotica virgifera LeConte, collected from two widely separated areas in Nebraska, were assayed for susceptibility to aldrin, Diazinon® (O,O-diethyl O-(2-isopropyl-4-methyl-6-pyrimidinyl) phosphorothioate), and heptachlor. Dosage-mortality curves and LD₅₀ values were determined for each insecticide. Results indicated that adults of D. virgifera collected from the central part of the State required about 100 times as much aldrin or heptachlor per insect to produce an LD₅₀in 2 hours as adults collected in eastern Nebraska. LD₅₀ values for Diazinon tested on beetles from the two areas were virtually the same. The reasons for such differential resistance are considered.