# Rapid Artificial Infestation Method for Assessing Fall Armyworm (Spodoptera frugiperda) Damage on Maize

## TL;DR

A new method allows quick assessment of how well genetically modified maize resists fall armyworm pests in lab, greenhouse, and field settings.

## Contribution

A rapid, standardized infestation protocol for evaluating maize resistance to fall armyworm across multiple environments.

## Key findings

- Infesting maize with early-instar larvae allows accurate resistance assessment within 10–12 days.
- The method reduces evaluation costs and timelines while providing standardized guidance for transgenic maize testing.

## Abstract

The fall armyworm is a destructive pest that has spread globally, causing severe damage to crops such as maize. Scientists have developed genetically modified maize to resist this pest; however, assessing its effectiveness requires efficient and reliable evaluation methods. This study aimed to establish a simple and rapid assessment protocol suitable for laboratory, screenhouse, and field environments. We found that infestation of maize plants with a defined number of early-instar larvae allows accurate assessment of plant resistance within approximately 10–12 days. This method reduces costs and shortens the evaluation timeline, while providing practical and standardized operational guidance for evaluating insect-resistant transgenic maize.

The fall armyworm (Spodoptera frugiperda) is a globally invasive pest that threatens the yield of maize and other grain crops. Transgenic insect-resistant maize offers an effective management strategy; however, rigorous evaluation of resistance to it depends on rapid and standardized infestation protocols. We developed and benchmarked laboratory, screenhouse, and field methods for rapid resistance assessment using 1–4-day-old larvae (L1–L4) and maize whorl leaves, silks, and kernels as feeding substrates. In laboratory bioassays, five L2 on each leaf or silk treatment enabled resistance assessment on day 2 post-infestation, whereas two L1 per treatment on kernels supported evaluation on day 3. In screenhouse trials, infesting each plant with twenty L2 allowed reliable leaf-injury ratings on day 10. In field trials, thirty L3 per plant with assessment on day 12 produced better outcomes. Together, these protocols provide a detailed and adaptable framework that reduces costs, shortens evaluation timelines, and offers practical guidance for resistance assessment of transgenic maize across controlled and open environments.