Contact Toxicity, Electrophysiology, Anti-Mating, and Repellent Effects of Piper guineense Against Spodoptera frugiperda (Lepidoptera: Noctuidae)

The fall armyworm, <i>Spodoptera frugiperda</i>, is a long-distance migratory pest, which invaded the African continent in 2016, causing enormous losses to agricultural crops, especially maize. Synthetic insecticides are primarily used for managing <i>S. frugiperda</i>, but they leave residues on human food and animal feed and also cause environmental hazards. We evaluated the crude ethanolic extract of <i>Piper guineense</i> fruits for contact toxicity on <i>S. frugiperda</i> larvae and determined the lethal concentration (LC₅₀) of the extract. Additionally, we conducted an electrophysiological (EAG) experiment to determine the responses of adult <i>S. frugiperda</i> males and females to <i>P. guineense</i> and determined whether the extract influenced mating, oviposition, and repellence to the adult female. We found that <i>P. guineense</i> extract caused significantly higher mortality to <i>S. frugiperda</i> larvae than an ethanol control. Electrophysiologically, we observed significantly higher responses to the extract than the control, with some variations in response between the sexes. A wind tunnel experiment revealed that females moved more towards the control than towards the extract. Taken together, our results confirm that <i>P. guineense</i> extract is effective against <i>S. frugiperda</i> larvae and adults. Future research should explore the responses of <i>S. frugiperda</i> to <i>P. guineense</i> extract on a field scale.