Plants respond to insect attack by emission of volatile organic compounds, which recruit natural enemies of the attacking herbivore, constituting an indirect plant defence strategy. In this context, the egg parasitoid Trissolcus basalis is attracted by oviposition-induced plant volatiles emitted by Vicia faba plants as a consequence of feeding and oviposition by the pentatomid host Nezara viridula. However, this local tritrophic web could be affected by the recent invasion by the alien pentatomid bug Halyomorpha halys, an herbivore that shares the same environments as native pentatomid pests. Therefore, we investigated in laboratory conditions the possible impact of H. halys on the plant volatile-mediated signalling in the local tritrophic web V. faba–N. viridula–T. basalis. We found that T. basalis wasps were not attracted by volatiles induced in the plants by feeding and oviposition activities of H. halys, indicating specificity in the wasps’ response. However, the parasitoid attraction towards plant volatiles emitted as a consequence of feeding and oviposition by the associated host was disrupted when host, N. viridula, and non-associated host, H. halys, were concurrently present on the same plant, indicating that invasion by the alien herbivore interferes with established semiochemical webs. These outcomes are discussed in a context of multiple herbivory by evaluating the possible influences of alien insects on local parasitoid foraging behaviour.

中文翻译：

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侵入性昆虫食草动物破坏了植物挥发物介导的三营养信号。

植物通过排放挥发性有机化合物来对昆虫的攻击作出反应，这些有机化合物招募了攻击性草食动物的天敌，构成了间接的植物防御策略。在这种情况下，卵寄生的Trissolcus basalis卵被蚕豆寄主产的Nezara viridula取食和产卵的结果，吸引了由蚕豆产生的产卵诱导的植物挥发物。但是，该本地三营养网可能受到外来五倍体昆虫Balyomorpha halys最近入侵的影响，该草食动物与天然五倍体害虫具有相同的环境。因此，我们在实验室条件下调查了H. halys的可能影响在当地的三重营养网的植物挥发介导的信号蚕豆- N.蝽- T.基蜕膜。我们发现T. basalis黄蜂没有被H. halys的进食和产卵活动诱导的挥发物吸引，这表明黄蜂的反应具有特异性。然而，当寄主N. viridula和非寄主H. halys破坏了由于寄主的摄食和产卵而导致的寄生虫对植物挥发物的吸引。，同时存在于同一棵植物上，表明外来草食动物的入侵会干扰已建立的化学信息网。通过评估外来昆虫对当地寄生虫觅食行为的可能影响，在多种食草动物的背景下讨论了这些结果。