Wilting speed affects drought-herbivore interactions in soybean with consequences for fitness

Soybean (Glycine max (L.) Merr.) is a vital food source for both humans and livestock and is also a key crop in global oilseed production. Drought is a challenge in soybean production in the field, causing a significant reduction in yield in as few as 96 hours. However, a reduction in yield is only one of the destructive aspects of drought. In some instances, drought can increase pest incidence and make plants more palatable for insect herbivores. There are significant differences in the physiology of soybean genotypes with differing wilting speeds which each alter plant-insect interactions. Increased drought incidence makes it vital to understand how herbivores interact with soybean plants of differing wilting speeds under drought conditions to better examine how water use efficiency traits influence plant-insect interactions. Fall armyworm (Spodoptera frugiperda, FAW) is a major pest worldwide and a growing concern for soybean production. Neonatal FAW were placed on an artificial diet that incorporated soybean leaves collected from both fast and slow wilting soybean accessions with and without exposure to drought treatments and reared to adulthood to determine the impacts of drought on insect pest development. Results show that there is significantly higher mortality of FAW on soybean plants that did not experience drought treatment compared to plants that did experience drought. FAW gained more mass on slow wilting soybeans across both treatments compared to fast wilting soybeans. These results indicate that FAW experienced higher mortality on healthy soybean plants compared to drought stressed plants.