Optimizing Rearing of Helicoverpa zea: Impacts of Pupal Maturity, Emergence Synchrony, and Adult Cohort Size

The bollworm/corn earworm, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae), is one of the most economically damaging crop pests in North America. Colonies of H. zea are notoriously difficult to maintain and frequently collapse in laboratory rearing. The persistent difficulty in maintaining healthy H. zea colonies has become a major obstacle to performing many research activities on the insect. To optimize colony maintenance, six populations were evaluated across three trials and six tests examining pupal maturity at diet removal, adult emergence synchrony, and cohort size at mating and reproduction. Females emerging from mature pupae produced more eggs than those from mid-aged (5-7 d) or young pupae (0-2 d). Synchronizing male and female emergence within one day yielded higher mating frequency, spermatophore transfer, and progeny, whereas a two-day difference reduced these metrics by 45-67%. Adult cohort size also influenced the outcomes, with ≥10 males and ≥10 females per cage enhancing reproductive success. Most matings occurred on nights 2-3, peaking within 2.5 h after lights off. Positive correlations were observed among mating frequency, spermatophore transfer, and progeny production. Overall, optimal performance was achieved by removing pupae only at maturity, synchronizing adult emergence within one day, and maintaining larger adult cohorts. These findings should establish key conditions to improve the mating success, reproduction, and laboratory rearing of H. zea.