Aphids betrayed by their odours

To fight against crop ravagers, such as the aphid, whilst restricting the use of pesticides, one of the solutions consists of attracting their predators to where these insects proliferate. One of the pathways being explored to achieve this goal consists of extracting molecules which have an odour, emitted by the aphids and detected by their predators, and releasing them in the fields. Amongst these molecules is numbered the aphid alarm pheromone, and it is this that ULg researchers have looked into.

They are invisible to the naked eye yet govern a good number of behavioural patterns in the animal and plant kingdoms. Humanity itself, despite its developed cognitive capacities and its tendency to want to control everything, today remains dependent on these ‘sovereign molecules.’ The ones which have the power to influence animal and plant behaviour, dragging them along by the nose, are called pheromones. These chemical substances, often volatile, emitted by the majority of animals and certain plants, act as messengers between the individuals of the same species.

coccinelle puceron

An alarm odorant when confronted by predators

At the root of a veritable chemical communication, pheromones are classed according to the types of information they carry. Amongst them are numbered territorial pheromones, sexual pheromones, aggregation pheromones, trail pheromones and alarm pheromones. It was the latter which was looked into by Professor Eric Haubruge and François Verheggen, first assistant, of the Gembloux Agro-Bio Tech (University of Liège) Functional and Evolutive Entomology Unit. On the strength of their experience in this research field, the two scientists were called upon to write a chapter on alarm pheromones in the animal kingdom, published in Volume 83 of ‘Vitamins and Hormones’, dedicated to pheromones in the broadest sense (1). ‘We have worked a lot on insect crop ravagers,’ explains François Verheggen. ‘They use these odours to inform their congeners of the discovery of a food source, that they are looking for a sexual partner, but also to warn them about the presence of predators. In this case the message is quite simple: ‘I’m being attacked. Flee!,’ continues the researcher.

(1) Verheggen, F., Haubruge, E., & Mescher, M. (2010). Alarm pheromones. In G., Litwack (Ed.), Pheromones. Vitamins and Hormones series, Vol 83, Elsevier press. ISBN 978-0-12-381516-3.   

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