Assistant Professor, Entomology University of Illinois Champaign, Illinois
Flood (abiotic) stress coupled with herbivory (biotic) stress on a tomato plant can cause a direct impact on the physiology of the plant, and an indirect impact on the caterpillar pest itself. Given that plants will likely face both of these types of stressors simultaneously in nature, a better understanding of the impact on how these stressors interact with one another is needed. In this study we tested how flood stressed plants had an indirect impact on the growth and performance of two economically important pest species of tomato; Spodoptera exigua (lepidoptera: Noctuidae) A Genralist and a specialist Manduca sexta (Lepidoptera: Sphingidae). We compared herbivore performance and growth of these two species by feeding them one of three different treatments of tomato plants: Flooded, after-flood, or a control non-flooded treatment. Our results showed that Manduca sexta (specialist) followed a clear trend of performing best on after-flood and flood treatments by growing at a faster rate than those feeding on the non-flooded treatment (control). In contrast, when viewing the data for growth and performance, no clear trends were observed for Spodoptera exigua (generalist). Taken together our results highlight the importance of understanding the interrelationships of flood stress and herbivore growth and suggest that flood stress could have an indirect impact on herbivore performance. Future experiments intend to understand the mechanisms underpinning the differential growth and performance results between the specialist and generalist and examining how flood stress impacts larval feeding preference.