Bottom-up effect of water stress on the aphid parasitoid <em>Aphidius ervi</em>

Description

Parasitoids inhabiting agro-ecosystems may be largely affected by bottom-up forces, notably owing to abiotic stresses, and this may modulate parasitoids preference (host acceptance) and/or their performance (host suitability). The availability of water is a key factor impacting plant quality and in determining changes in plant-insect community structure. In the present study, we have examined the bottom-up effects of water stress on host specificity of the aphid parasitoid Aphidius ervi (Hymenoptera: Braconidae). The cascade impact of water stress on host plants varied with the aphid-plant systems considered. Water stress applied to bean did not impact the performance of A. ervi on Acyrthosiphon pisum whereas it negatively affected the parasitoid on Sitobion avenae on wheat. The wheat leaf mass per area was higher on water-stressed plants than on the well-watered ones, no effect on this trait was observed on bean plants when subjected to water stress. Various mechanisms, notably possible variations in the production of plant toxins as well as varying aphid quality (host) during water stress are discussed to explain the bottom-up effects on parasitoids.

Abstract

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