D3071: Investigating the impact of drought stress on trophic interactions and biological control

Climate change is causing drought events to increase throughout the world in both intensity and occurrence, and the resulting water-limitation is expected to have widespread ecosystem effects. Drought-induced changes in plant physiology are known to affect the quantity and quality of insect herbivores, which can have cascading effects for natural enemies by reducing host or prey quality. Sap-feeding insects like aphids are known to perform poorly on water-limited plants, but parasitoid success varies depending on the intensity of plant water stress and may be related to changes in host quality. The preference-performance hypothesis predicts that females will preferentially choose the best host for their young, but it is unclear how plant water stress modifies this prediction. Given that plant drought stress is known to reduce herbivore fitness, natural enemies like parasitoid wasps may preferentially not oviposit into hosts feeding on water-stressed plants due to poor host quality. The objective of our work is to understand whether the parasitoid wasp Aphidius colemani demonstrates preference between bird cherry-oat aphids (Rhopalosiphum padi) previously feeding on wheat plants (Triticum aestivum) subjected to one of three levels of water availability, and whether wasp preference matches their performance. We measured wasp choice when presented with aphids previously fed on plants grown with multiple levels of water stress. Our work will contribute to a greater body of knowledge about how insects and trophic interactions are being affected by climate change, as well as a broader understanding of how parasitoid wasps choose their hosts.