Comparison of Three Sampling Methods for Monitoring Adult European Corn Borer (Lepidoptera: Pyralidae) Population Trends1

Two relative methods of sampling Ostrinia nubilalis (Hubner) adults, blacklight trap (BLT) and flush bar (FB), were compared with the more absolute drop-net (DN) method over four flights in central and eastern Iowa (1980–1981). Although light traps showed similar population trends regardless of proximity to cornfields or action sites (aggregations of adults in dense grass), the trends were not the same as those shown by the DN. The FB method, however, showed trends similar to those of the DN, and this sampling procedure can replace the DN during the critical period (first 12 to 17 days) of a moderate to heavy flight. An average of 61 European corn borer adults per 10 m2, indicated by the new FB sampling method, was equivalent to the DN threshold average of 3 European corn borer females per 1 m2 of action site (dense grass) previously established and reported in the literature.