Under pressure: Investigating how plant water stress impacts parasitoid-host interactions

As extreme drought events increase around the world, understanding the impacts of water limitation on plant-insect systems becomes increasingly essential for preserving our ecosystems and controlling agricultural pests. Although physiological changes from water limitation are predicted to make plants more nutritious for insect herbivores, it comes at the cost of increased plant defensive responses, declining biomass, and most notably, restricted access to the phloem from reduced turgor pressure. These changes in the plant have direct effects on natural enemies by changing the attractiveness of the habitat, and indirect effects by changing prey quality through reduced herbivore fitness. Our goal is to assess how changes in plant quality from different levels of water limitation indirectly affect parasitoid wasps as mediated through their aphid host. We found that the level of water stress does affect both preference and performance, but the mechanisms for these differences are still unclear. Current work is focused on assessing how wasp performance and aphid suppression are directly affected by changes in plant water potential. We released wasps into aphid populations on plants experiencing a gradient of water potential conditions and assessed wasp pupae formation, wasp emergence, wasp size, and aphid populations size. This work aims to reveal how parasitoid-aphid relationships are affected by drought water stress and will inform how we manage agricultural and natural ecosystems in drought conditions.