Could vectors\u2019 fear of predators reduce the spread of plant diseases?

G Tholt,É Szita,A Medzihradszky,Z Havelda,F Samu,A Kis,Z Tóth

doi:10.1038/s41598-018-27103-y

Abstract

Predators influence the behaviour of prey and by doing so they potentially reduce pathogen transmission by a vector. Arthropod predators have been shown to reduce the consumption of plant biomass by pest herbivores, but their cascading non-consumptive effect on vector insects’ feeding behaviour and subsequent pathogen transmission has not been investigated experimentally before. Here we experimentally examined predator-mediated pathogen transmission mechanisms using the plant pathogen Wheat Dwarf Virus that is transmitted by the leafhopper, Psammotettix alienus. We applied in situ hybridization to localize which leaf tissues were infected with transmitted virus DNA in barley host plants, proving that virus occurrence is restricted to phloem tissues. In the presence of the spider predator, Tibellus oblongus, we recorded the within leaf feeding behaviour of the herbivore using electrical penetration graph. The leafhopper altered its feeding behaviour in response to predation risk. Phloem ingestion, the feeding phase when virus acquisition occurs, was delayed and was less frequent. The phase when pathogen inoculation takes place, via the secretion of virus infected vector saliva, was shorter when predator was present. Our study thus provides experimental evidence that predators can potentially limit the spread of plant pathogens solely through influencing the feeding behaviour of vector organisms.

Highlights

Predation can induce important density and trait mediated effects on prey populations which have the potential to cascade through entire food webs and lead to ecosystem-wide effects[1,2]
It is likely that the sap feeder guild of insects have undergone similar evolutionary pressures to avoid predation, studies of non-consumptive effects (NCEs) on sap feeders have been limited to movement and escape behaviours and were missing information about the actual feeding process
If the complex sap feeding behaviour is responsible for the acquisition and inoculation of plant pathogens, the NCEs of predators has a role of particular importance, as indirect trait mediated effects may impact the level of herbivory, but may interrupt specific steps in the feeding process and thereby suppress the transmission and epidemic of plant diseases[14]

Summary

Introduction

Predation can induce important density and trait mediated effects on prey populations which have the potential to cascade through entire food webs and lead to ecosystem-wide effects[1,2]. SS feeders have to balance predator avoidance against their minimal nutritional requirements when engaged in feeding behaviour. This suggests that longer feeding times increase exposure to predators, while delaying or shortening feeding times raises the risks of desiccation and starvation[11]. If the complex sap feeding behaviour is responsible for the acquisition and inoculation of plant pathogens, the NCEs of predators has a role of particular importance, as indirect trait mediated effects may impact the level of herbivory, but may interrupt specific steps in the feeding process and thereby suppress the transmission and epidemic of plant diseases[14]

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Conclusion