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

## TL;DR

This study identifies optimal conditions for rearing Helicoverpa zea in the lab, focusing on pupal maturity, synchronized emergence, and large adult groups to improve mating and reproduction.

## Contribution

The study provides specific, actionable guidelines for improving laboratory rearing of Helicoverpa zea through controlled biotic factors.

## Key findings

- Removing pupae only at maturity increases egg production in females.
- Synchronizing male and female emergence within one day boosts mating and reproduction metrics.
- Larger adult cohorts (≥10 per sex) enhance reproductive success in Helicoverpa zea.

## Abstract

The bollworm/corn earworm (Helicoverpa zea) is a major crop pest, but laboratory rearing challenges limit research progress. This study tested three selected biotic factors, pupal maturity, adult emergence synchrony, and adult cohort size that influence mating and reproduction. Results show that reproductive success is optimized when pupae are removed only at maturity, males and females emerge within one day of each other, and adult groups are kept large (≥10 of each sex per cage). These insights provide useful information to improve the mating, reproduction, and long-term laboratory colony maintenance of H. zea.

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.