Rapid Infestation and Evaluation Methods for Assessing Fall Armyworm (Spodoptera frugiperda) Damage on 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, yet rigorous evaluation of resistance to it depends on rapid, particular infestation protocols. We developed and benchmarked laboratory, screenhouse, and field methods for assessing rapidly resistance using larvae aged 1–4 days post-hatch (D1–D4) and maize whorl leaves, silks, and kernels as feeding substrates. In laboratory bioassays, five D2 larvae per treatment on leaves or silks enabled resistance assessment on day 2 post-infestation, whereas two D1 larvae per treatment on kernels supported evaluation on day 3. In screenhouse trials, infesting each plant with twenty D2 larvae allowed reliable leaf-injury ratings on day 10. In field trials, thirty D3 larvae 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.