Drought and Root Herbivory Interact to Alter the Response of Above-Ground Parasitoids to Aphid Infested Plants and Associated Plant Volatile Signals

Abstract

Multitrophic interactions are likely to be altered by climate change but there is little empirical evidence relating the responses of herbivores and parasitoids to abiotic factors. Here we investigated the effects of drought on an above/below-ground system comprising a generalist and a specialist aphid species (foliar herbivores), their parasitoids, and a dipteran species (root herbivore).We tested the hypotheses that: (1) high levels of drought stress and below-ground herbivory interact to reduce the performance of parasitoids developing in aphids; (2) drought stress and root herbivory change the profile of volatile organic chemicals (VOCs) emitted by the host plant; (3) parasitoids avoid ovipositing in aphids feeding on plants under drought stress and root herbivory. We examined the effect of drought, with and without root herbivory, on the olfactory response of parasitoids (preference), plant volatile emissions, parasitism success (performance), and the effect of drought on root herbivory. Under drought, percentage parasitism of aphids was reduced by about 40–55% compared with well watered plants. There was a significant interaction between drought and root herbivory on the efficacy of the two parasitoid species, drought stress partially reversing the negative effect of root herbivory on percent parasitism. In the absence of drought, root herbivory significantly reduced the performance (e.g. fecundity) of both parasitoid species developing in foliar herbivores. Plant emissions of VOCs were reduced by drought and root herbivores, and in olfactometer experiments parasitoids preferred the odour from well-watered plants compared with other treatments. The present work demonstrates that drought stress can change the outcome of interactions between herbivores feeding above- and below-ground and their parasitoids, mediated by changes in the chemical signals from plants to parasitoids. This provides a new insight into how the structure of terrestrial communities may be affected by drought.

Herbivore‐induced plant volatiles accurately predict history of coexistence, diet breadth, and feeding mode of herbivores

“…S6). This means that specific aphid parasitoids, such as Diaeretiella rapae for B. brassicae or Aphidius colemani for M. persicae , can also use HIPVs to discriminate hosts from nonhosts (Tariq et al ., ). Moreover, our data also support the postulate that specialist aphids are better able to suppress induced responses, such as HIPVs, that may attract their natural enemies (Züst & Agrawal, ).…”

Evaluation of Different Integrated Pest Management Modules to Control Helicoverpa for Adaptation to Climate Change

“…Our results show that parasitism of H. armigera was lower in water-stressed plant than irrigated plants. Similar behaviour of Aphidius colemani (Viereck) and A. ervi (Haliday) had been reported with drought (Tariq et al, 2013). Similarly, mango mealybug parasitism was recorded to be low under drought condition than irrigated condition (Calatayud et al, 2002).…”

Impact of predicted precipitation scenarios on multitrophic interactions

“…In contrast, published studies report significant effects of changes in plant water status on the population of mummified aphids (Aslam, Johnson & Karley ; Tariq et al . ). However, these studies were conducted in a controlled environment glasshouse.…”

“…; Aslam, Johnson & Karley ; Tariq et al . ) and do not consider how this will influence insect herbivore quality as prey for insect predators. Moreover, the majority of research is conducted in controlled environment systems.…”