Data underlying the publication: Enhanced parasitisation of caterpillars and aphids on field-grown Brassica oleracea plants upon soil amendment with insect exuviae

Multitrophic plant-insect interactions are mediated by plant volatiles. The emission of herbivore-induced plant volatiles is influenced by environmental conditions, such as soil microbes and nutrient composition, with consequences for aboveground trophic interactions. Here we investigated whether insect exuviae in the soil alter the plant’s volatile blend and attraction of parasitoids in the laboratory and whether this attraction also occurs in the field.We studied the effects of soil amendment with exuviae originating from three insect species, Tenebrio molitor, Acheta domesticus, and Hermetia illucens, on the proportion of parasitised Plutella xylostella caterpillars and Brevicoryne brassicae aphids in the field in three consecutive years. In the laboratory, we collected and analysed the volatile blend of amended plants infested with caterpillars or aphids. The attraction of the parasitoids Diadegma semiclausum and Diaeretiella rapae, respectively, towards these volatile blends was assessed in an olfactometer.Our study shows that insect exuviae amended soil enhanced the proportion of parasitised herbivores of two species in the field. Relative amounts of several components of the plant volatile blend were affected by soil amendment. Soil amendment with Acheta domesticus or Tenebrio molitor exuviae resulted in increased attraction of the two parasitoid species in the olfactometer.Soil amendment with insect exuviae altered the plant volatile blend leading to enhanced attraction of parasitoids in laboratory assays. These effects were sustained under the complex and variable biotic and abiotic conditions in the field. Our results underline the importance of belowground processes, such as the decomposition of insect exuviae, on aboveground volatile-mediated multitrophic interactions.

多营养级植物-昆虫互作由植物挥发性物质所介导。植食性昆虫诱导的植物挥发性物质的释放受到环境条件（如土壤微生物与养分组成）的影响，并进而影响地上营养级互作。本研究旨在探究土壤中的昆虫蜕是否会改变植物的挥发性混合组分，并在实验室条件下影响寄生蜂的趋性，同时验证该趋性效应是否在野外环境中同样存在。本研究连续三年在野外开展实验，探究施加源自黄粉虫（Tenebrio molitor）、家蟋蟀（Acheta domesticus）与黑水虻（Hermetia illucens）三种昆虫蜕的土壤改良措施，对被寄生小菜蛾（Plutella xylostella）幼虫以及甘蓝蚜（Brevicoryne brassicae）占比的影响。在实验室条件下，本研究收集并分析了经土壤改良处理且被幼虫或蚜虫侵染的植物的挥发性混合组分，并通过嗅觉仪分别测定了菜蛾盘绒茧蜂（Diadegma semiclausum）与萝卜蚜茧蜂（Diaeretiella rapae）对上述挥发性混合组分的趋性反应。本研究结果表明，施加昆虫蜕的土壤可提升野外两种植食性昆虫的被寄生率。土壤改良措施会改变植物挥发性物质组分的相对含量。施加家蟋蟀或黄粉虫蜕的土壤改良措施，可在嗅觉仪实验中提升两种寄生蜂对植物挥发性组分的趋性。施加昆虫蜕的土壤改良措施可改变植物的挥发性物质组分，进而在实验室实验中增强寄生蜂的趋性。该效应在野外复杂多变的生物与非生物环境条件下仍可维持。本研究结果强调了地下过程（如昆虫蜕的分解）对地上由挥发性物质介导的多营养级互作的重要性。