Alarm pheromone causes aphids to sprout wings

Chemical communication within insect species is often much more sophisticated than expected. When aphids are attacked by predators such as ladybird beetles, they release an alarm pheromone, (E)-â-farnesene, that has long been known to cause other aphids to walk around or drop from the plant.

In a paper soon to appear in Ecology Letters, researchers at the University and Max-Planck-Institute in Jena, Germany, now show that exposure to alarm pheromone also causes pea aphids to produce winged offspring that leave their host plant when mature. Because some plants can also release (E)-â-farnesene, they could in theory manipulate aphids into flying away.

However, aphids were shown to react mainly to the frequency of pheromone release and not the actual quantity present, possibly to avoid manipulation by plants. Thus, to reduce damage caused by aphids, the major insect pests in Europe, it may prove effective to apply pulses of alarm pheromone to infested fields.

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