Plants produce distinct blends of volatile compounds that attract pollinators (floral odors) or natural enemies of insect herbivores (herbivore-induced plant volatiles). The admixture of these blends in the atmosphere may alter the attraction of insect mutualists and ultimately affect plant fitness. Here, using synthetic blends of Brassica rapa floral volatiles and real B. rapa flowers, we investigated how floral odors impact the foraging behavior of parasitoids. In an olfactometer setting, floral odors reduced the attractiveness of plants infested by herbivores to parasitoids by 43.5% and affected four out of five parasitoid species tested. Additionally, experiments with the parasitoid Cotesia glomerata revealed that the effects of floral odors are dose-dependent and that floral odors were less disruptive under wind tunnel conditions than under olfactometer conditions. Electroantennogram recordings showed that C. glomerata antennae do respond to floral compounds, but that floral compounds do not inhibit antennal responses to herbivore-induced leaf volatiles. In conclusion, floral odors can act as background pollutants decreasing the attractiveness of chemical blends used by natural enemies to locate their hosts. Under natural conditions, such interferences could affect the outcome of tritrophic interactions and may play an important role in the evolution of plant volatile signaling.

中文翻译：

---

花香会干扰寄生蜂寻找寄主的觅食行为

植物产生独特的挥发性化合物混合物，吸引传粉者（花香）或昆虫食草动物的天敌（食草动物诱导的植物挥发物）。这些混合物在大气中的混合可能会改变昆虫共生者的吸引力，并最终影响植物的健康。在这里，我们使用芸苔花挥发物和真正的白菜花的合成混合物研究了花香如何影响寄生蜂的觅食行为。在嗅觉仪设置中，花香使受食草动物侵扰的植物对寄生蜂的吸引力降低了 43.5%，并影响了五分之四的受测寄生蜂物种。此外，用寄生蜂 Cotesia glomerata 进行的实验表明，花香的影响是剂量依赖性的，在风洞条件下，花香的破坏性比在嗅觉计条件下要小。触角电图记录显示 C. glomerata 触角确实对花化合物有反应，但花化合物不抑制对食草动物诱导的叶挥发物的触角反应。总之，花香可以作为背景污染物，降低天敌用来定位宿主的化学混合物的吸引力。在自然条件下，这种干扰会影响三营养相互作用的结果，并可能在植物挥发性信号的进化中发挥重要作用。glomerata 触角确实对花化合物有反应，但花化合物不抑制对食草动物诱导的叶挥发物的触角反应。总之，花香可以作为背景污染物，降低天敌用来定位宿主的化学混合物的吸引力。在自然条件下，这种干扰会影响三营养相互作用的结果，并可能在植物挥发性信号的进化中发挥重要作用。glomerata 触角确实对花化合物有反应，但花化合物不抑制对食草动物诱导的叶挥发物的触角反应。总之，花香可以作为背景污染物，降低天敌用来定位宿主的化学混合物的吸引力。在自然条件下，这种干扰会影响三营养相互作用的结果，并可能在植物挥发性信号的进化中发挥重要作用。