Indirect effects of banker plants through herbivory-induced plant volatiles

Abstract: Secondary plants are widely used to enhance the effectiveness of biological control
programs. A kind of spider flowers, Cleome hassleriana, is often used as a banker plant for the zoophytophagous mirid bug Nesidiocoris tenuis that is employed as biological control agent against whiteflies and thrips. Many zoophytopahous mirid bugs inject saliva to digest plant tissue and such a wounding mechanism induce plant defence systems. Many studies reported that plants fed by N. tenuis release plant species-specific N. tenuis-HIPVs (Nt-HIPVs) which facilitate plant-plant communication. However, it is unknown whether Nt-HIPVs from banker plants affect the performance of herbivores. We investigated whether exposure of Nt-HIPVs or HIPVs induced by the two-spotted spider mite Tetranychus urticae (Tu-HIPVs) from C. hassleriana to tomato plants affects survival and oviposition of T. urticae on tomato plants. Results showed that induced defences of tomato plants facilitated by Tu-HIPVs reduced the number of eggs laid by T. urticae, but not in case of exposure to Nt-HIPVs. Our results demonstrate that Tu-HIPVs from C. hassleriana can induce plant defence response and reduce T. urticae performance. Therefore, C. hassleriana may not only maintain the population of N. tenuis, but also serve as a dispenser to release HIPVs that activate the defence of tomato plants.