Silicon (Si) accumulation in plants is widely recognised as an effective physical defence against chewing herbivores. However, its effects on some feeding guilds such as cell-content feeders are understudied despite being severe economic pests (e.g. Tetranychus urticae). Moreover, most studies focus on direct impacts of Si, but there is growing evidence that Si also impacts indirect defence. We examined the effects of Si on French bean, Phaseolus vulgaris, defences against the two-spotted spider mite, T. urticae. We grew plants hydroponically with (+ Si) or without (–Si) silicon, assessed T. urticae performance and tested the preference of the predatory mite, Phytoseiulus persimilis, for volatiles from T. urticae-infested (+ M) or uninfested (–M) plants. The provision of Si to plants suppressed T. urticae egg-laying, population growth and leaflet damage, and partially ameliorated T. urticae-induced reductions in stomatal conductance and net photosynthesis. Furthermore, T. urticae infestation increased foliar Si accumulation. Predatory mites were more attracted (64%) to volatiles from + Si plants experiencing herbivory than to –Si plants. The relative emissions (%) of volatile compounds, viz. E-2-hexanyl benzoate, hexanal, E-trans-β-ocimene, D-limonene, β-caryophyllene and methyl salicylate were elevated from + Si + M plants, while the relative emissions of 3-hexanol, trans-calamenene, o-xylene and o-cymene were lowered compared to –Si + M plants. Our results show, for the first time, that Si defences are inducible and effective even in low Si-accumulating plants against T. urticae and suggest that Si could play a role in pest biocontrol.

植物中的硅（Si）积累被广泛认为是抗嚼草食动物的有效物理防御。然而，尽管它是严重的经济害虫（例如，Tetranychus urticae），但它对某些饲养行会（如细胞含量饲养器）的影响仍未得到充分研究。此外，大多数研究都集中在Si的直接影响上，但是越来越多的证据表明Si也影响间接防御。我们研究了Si对菜豆菜豆（Phaseolus vulgaris）的防御作用，以及对两斑叶螨（T. urticae）的防御作用。我们使用（+ Si）或不使用（–Si）硅对植物进行了水培，评估了荨麻疹的表现，并测试了捕食性螨（Phytoseiulus persimilis）对来自以下物种的挥发物的偏好荨麻疹（T. urticae）侵染（+ M）或未侵染（–M）植物。向植物中提供硅可抑制荨麻疹的产卵，种群增长和小叶损伤，并部分缓解荨麻疹引起的气孔导度和净光合作用的降低。此外，荨麻疹的侵染增加了叶片硅的积累。捕食性螨比-Si植物更容易吸引（64％）食草性+ Si植物的挥发物。挥发性化合物的相对排放量（％），即。E + -2-己基苯甲酸，己醛，E-反式-β-烯丙基，D-柠檬烯，β-石竹烯和水杨酸甲酯从+ Si + M植物中升高，而3-己醇，反式与-Si + M植株相比，降低了-a草烯，邻二甲苯和邻-cy烯的含量。我们的研究结果首次表明，即使在低硅积累量的植物中，硅防御也可诱导和有效地抵抗荨麻疹，并表明硅可能在害虫的生物防治中发挥作用。