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Putting plant signals to work

Man has used insect-repellent plant scents including citronella and lavender oils - for many centuries to repel unwanted house visitors and biting insects. Extensive research is revealing a vast array of insect repellent natural plant compounds. The research programme widens the olfactive range of perfumes available.
Quest perfumers can now formulate new floral scents that not only appeal to the human nose but, retaining the properties of citronella, offer effective, broad ranging insect repellency. These fragrances are incorporated into consumer products: moisturising cream, cologne and household cleaners that keep nuisance insects at bay.

At Imperial College at Wye, we have spent over ten years examining mixtures of natural plant compounds that are repellent to mosquitoes. To develop and test these materials, hungry mosquitoes are introduced into a wind tunnel containing warmed attractive targets at one end. Some of these targets are coated with plant scents and the number of mosquitoes landing recorded. Once significant repellency is shown, further testing is carried out to determine the best formulation that gives long lasting protection. Quest has now formulated effective new fragrances for mosquito-repellent products that are in the marketplace and used around the world.
In other tests, cockroaches are released into an arena with a floor, half of which has been treated with a cleaning cream containing plant scents. Using video analysis the numbers of cockroaches entering the treated area are recorded. Effective product formulations incorporating these fragrances repel both German and American cockroaches for up to 96 hours.