Tiadinil, a plant activator of systemic acquired resistance, boosts the production of herbivore-induced plant volatiles that attract the predatory mite Neoseiulus womersleyi in the tea plant Camellia sinensis.

Plants respond with various defense mechanisms to pathogenic or herbivorous attack. Some chemicals called plant activators that induce the plant defense response against pathogens have been commercially used to protect plants. Here we studied the effects of tiadinil (TDL) on defense mechanisms against herbivores. TDL suppresses pathogenic fungi on tea leaves by inducing defense mechanisms. We used one of the major trophic systems in tea consisting of the herbivorous mite, Tetranychus kanzawai, and the predatory mite, Neoseiulus womersleyi. TDL enhanced the production of herbivore-induced plant volatiles that attract predatory mites. The predatory mites preferred the T. kanzawai-induced volatiles from TDL-treated plants to those produced by untreated plants. These results suggest that TDL activates the plant defense response via an indirect process mediated by plant volatiles that attract natural enemies of the herbivores. In contrast, the oviposition rate, adult maturation rate, and sex ratio of T. kanzawai were not affected by TDL treatment. These results suggest that TDL did not activate any direct defense against the herbivorous mite.