| Aphids are major crop pests and can reduce yield up to 50 %. Infestations grow quickly to damaging levels, and yearly fluctuations in populations complicate decisions on insecticidal control measures. Use of conventional pesticides still threatens the agricultural landscape, causing environmental pollution and development of resistance by the aphids. There is a need for aphid management that delivers stable yields, is environmentally acceptable and sustainable over the long term.
In this project I will investigate how predator avoidance by an insect pest can contribute biological control. Colonisation of host plants is a key step in the development of aphid populations. We have recently shown that pest aphids can detect and avoid the chemical tracks left by one of their predators- ladybirds, reducing aphid host plant acceptance by up to 50%. Since ladybirds are highly mobile and search extensively for patchy aphid colonies walking on the plants, it could benefit plants to use ladybird presence as an indirect signal of imminent aphid attack, and respond by inducing defensive chemistry.
Aphid individuals that escape ladybird footprints lose feeding and mating opportunities and increase the risk to be captured by other predators. Thus disturbance by predators is a major factor in aphid mortality and this project will break new scientific ground. The project aims are to investigate how herbivore avoidance of predators contributes to biological control and how it can be exploited for sustainable crop protection.
The hypothesis is that chemical tracks deposited on plants by walking ladybirds affect aphids in ways that reduce their population. This can occur through two routes: directly by avoidance of the tracks and/or indirectly by avoidance of track-induced changes in the plant. I will (i) identify the mechanisms by which aphid avoidance of ladybird tracks disrupts their settling and population development and (ii) assess the contribution that predator avoidance makes to biological control. I will use advanced electrophysiological techniques to measure effects of ladybird tracks on aphid feeding, infrared thermography to study plant physiological responses and several different bioassays to assess aphid population disruption and olfactory responses.
This project will examine how aphid avoidance of ladybirds’ footprint contributes to biological control of aphids provided by predators based on an overlooked but important ecological interaction. In the longer term, increased effectiveness of ladybirds as biocontrol agents could be achieved by designing crop systems with specific enhancements in botanical diversity which encourage ladybird mobility within the crop stand.
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