Defense of pyrethrum flowers: repelling herbivores and recruiting carnivores by producing aphid alarm pheromone

What is it about?

Plants have been suspected to hijack insect alarm pheromones to their benefit, but without ecological evidence thus far. We found fields of pyrethrum flowers that were full of ladybird beetles, but without their aphid preys. Flower emission of the aphid alarm pheromone (E)-beta-farnesene (EβF) provided the cue to solve this puzzle. Pyrethrum flowers have evolved a form of defensive chemical mimicry in which the same molecule EβF is a deterrent to aphids and an attractant of aphid predators as a safety net.

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