Rapid Artificial Infestation Method 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; 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.