INSECTICIDE RESISTANCE AND RESISTANCE MANAGEMENT Development of Resistance to eCry3.1Ab-Expressing Transgenic Maize in a Laboratory-Selected Population of Western Corn Rootworm (Coleoptera: Chrysomelidae)

A laboratory colony of western corn rootworm,Diabrotica virgifera virgifera LeConte, was selected for resistance to transgenicmaize expressing the eCry3.1Ab protein. The selected colony was developed by rearing larvae on nonelite noncommercial Bt maize expressing the eCry3.1Ab protein. After four generations, selected and control colonieswere screened on eCry3.1Ab-expressing and isoline maize using greenhouse experiments. There was a signiÞcant colony maize pedigree interaction in terms of the number of larvae recovered. There was no signiÞcant difference in the number of larvae recovered from eCry3.1Ab-expressing and isoline maize for the selected colony, whereas this difference was signiÞcant for the control colony. There was not a signiÞcant colony maize pedigree interaction in terms of root damage, or the number of beetles recovered, but the effect ofmaizepedigreewas signiÞcant.After four andeight generationsof selection, seedlingbioassayswere performed. Again, therewas a signiÞcant colony maize pedigree interaction in terms of the number of larvae recovered. After 11 generations of selection, larvae from the selected colony had higher LC50 values than the control colony when exposed to increasing concentrations of the eCry3.1Ab protein. The resistance ratio of the selected colony was 2.58. These data provide necessary information for understanding the potential for Bt resistance by western corn rootworm and underscores the need for insect resistance management plans for this pest.