Effect of age and mating status on adult European corn borer (Lepidoptera: Crambidae) dispersal from small-grain aggregation plots.

The European corn borer, Ostrinia nubilalis (Hübner) (Lepidoptera: Crambidae), is often controlled with genetically modified corn, Zea mays L., hybrids (Bacillus thuringiensis [Bt] corn) in the United States. If Bt-resistant insects are detected in the field, mitigation-remediation tactics must be implemented to sustain the efficacy of insecticidal, transgenic corn. Mass releasing laboratory-reared, susceptible adults near aggregation sites to mate with locally emerging resistant adults is a possible remediation tactic, but it is imperative that the former remain in or near the release site long enough to mate. Understanding adult dispersal behavior relative to the timing of mating is important, because it directly affects patterns of gene flow and the rate at which Bt resistance moves through a population. Previous work shows that newly eclosed adults do not remain in proximity to their natal field. However, moth age, reproductive development, or mating status may influence the propensity to disperse. The objectives of this study were to determine the effect of adult age (0-3, 4-6, and 7-10 d old) and mating status on dispersal of adults released in small-grain aggregation plots. Less than 1% of the marked adults released in the aggregation plots remained after one night. More males than females were recovered. Age influenced dispersal, with mostly 4-6-d old adults being recovered. Conversely, mating status did not affect the number of adults recovered. Given the paucity of marked adult moths recovered near their release sites, mass releases of adults may not be a viable tactic to combat the spread of resistance to Bt corn.