The omnivorous predator Macrolophus pygmaeus induces production of plant volatiles that attract a specialist predator

It has become clear that omnivorous predators can induce plant defences that affect the performance and host plant choice of herbivores. They are also known to induce the production of plant volatiles that can affect the behaviour of herbivores searching for plants. These volatiles may also affect the searching behaviour of other predators, which was investigated here. The predatory mite Phytoseiulus persimilis preferred plants previously exposed to the omnivorous mirid Macrolophus pygmaeus over clean plants. The mites were equally attracted to plants previously exposed to the omnivore and subsequently infested by spider mites (Tetranychus urticae, prey of the predatory mite and the omnivore) and plants infested with spider mites alone. Moreover, the mites were more attracted to plants infested with prey and subsequently exposed to the omnivore than plants infested with prey but not exposed to the omnivore. The predatory mites were also significantly more attracted to plants on which the omnivores were still present. Experience of the predatory mites with volatiles from plants previously exposed to the omnivore and without prey resulted in a loss of the preference for volatiles emitted by plants exposed to the omnivore. Analysis of the volatiles showed that plant exposure to omnivores induced qualitative and quantitative changes in the volatile blend. Together, these results suggest that omnivorous predators induce the production of plant volatiles that can interfere with the searching behaviour of other predators. The consequences of such interference for biological pest control remain to be investigated