A comparison of the responses of Tetranychus urticae (Acari: Tetranychidae) and Phytoseiulus persimilis (Acari: Phytoseiidae) to volatiles emitted from lima bean leaves with different levels of damage made by T. urticae or Spodoptera exigua (Lepidoptera: Noctuidae)

Volatiles from lima bean leaves heavily infested with the herbivorous spider mite, Tetranychus urticae, attracted the carnivorous mite, Phytoseiulus persimilis, and repelled T. urticae over volatiles from uninfested leaves. Significantly more herbivore-induced volatiles were emitted from heavily infested leaves than from slightly infested leaves. When leaves were moderately infested, the amount of induced volatiles was intermediate between those of heavily infested and slightly infested leaves. These volatiles attracted P. persimilis, but neither attracted nor repelled T. urticae more than uninfested leaves. When leaves were slightly infested with T. urticae, small amounts of induced volatiles were detected. These volatiles neither attracted nor repelled P. persimilis more than uninfested leaves, but attracted T. urticae more than uninfested-leaf volatiles. The volatiles from lima bean leaves that were slightly or heavily infested with the herbivorous lepidopteran, Spodoptera exigua, neither attracted nor repelled T. urticae or P. persimilis. Most of the volatile compounds emitted from leaves heavily-infested with S. exigua were the same as those emitted from T. urticae-infested leaves, but the blend of the volatiles differed with the infesting species. The functions of volatiles emitted from herbivore-infested leaves are discussed in terms of herbivore density and their specificity.