Intact lima bean plants exposed to herbivore-induced plant volatiles attract predatory mites and spider mites at different levels according to plant parts

Previous studies have shown that intact lima bean plants exposed to volatiles emitted from conspecific plants infested by two-spotted spider mites, Tetranychus urticae (Acari: Tetranychidae), attract Phytoseiulus persimilis (Acari: Phytoseiidae), a carnivorous natural enemy of spider mites. Here, we investigated the olfactory responses of P. persimilis and T. urticae to different parts of intact lima bean plants exposed to these volatiles using a Y-tube olfactometer. Predators responded in greater number to volatiles from the first trifoliate leaves compared to those from primary leaves, and to volatiles from the parts above the first trifoliate leaves compared to those from the first trifoliate leaves. Conversely, spider mites responded more to volatiles from primary leaves compared to those from the first trifoliate leaves, and showed equal preference for volatiles released from the first trifoliate leaves or the parts above the first trifoliate leaf. The reproduction of spider mites in primary leaves was higher than those on trifoliate leaves. Based on these data, the potential adaptive value of differential attractiveness of different parts of intact lima bean plants to T. urticae and P. persimilis is discussed.