The Effect of Temperature on the Phenology of Fall Webworm

As global temperatures rise, climate change is expected to have significant effects on Earth’s ecosystems and insect populations. Specifically, heatwaves are starting to increase in intensity and frequency, which negatively impacts insects as insects are particularly sensitive to temperature variation. Increasing temperatures and heatwaves can affect plant-insect synchrony as well as the timing of important life-history events. The generalist insect herbivore fall webworm (Hyphantria cunea) is a moth species local to Colorado, and it can occur in diverse environments and feed upon a variety of host plants. It is known that fall webworm larvae can have considerable variance in their performance when reared on different host plants. It is unknown the extent to which the type of host plant affects the development of fall webworm larvae under different thermal conditions. This project investigated how fall webworm performance is affected by thermal stress (climate change) through elevated temperatures and heatwave conditions. Performance was measured by survival, development time, and pupal mass. Further, this project examined whether larval development and mortality vary depending on the type of host plant. The results suggest that increased temperatures had an overall negative effect, but that diet could mitigate these effects. Additionally, there was a significant interaction between host plant type and heatwave duration, which means that larval performance during a heatwave was dependent on host plant. This project supports the evidence that higher temperatures and heatwaves have negative effects on insect populations, but the extent may vary depending on quality of diet.