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, <em>Tenebrio molitor</em>, <em>Acheta domesticus</em>, and <em>Hermetia illucens</em>, on the proportion of parasitised <em>Plutella xylostella</em> caterpillars and <em>Brevicoryne brassicae</em> 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 <em>Diadegma semiclausum</em> and <em>Diaeretiella rapae</em>, 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 <em>Acheta domesticus</em> or <em>Tenebrio molitor</em> 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.<br>

植物挥发物介导了多营养级的植物-昆虫互作。植食性昆虫诱导的植物挥发物释放受环境条件（如土壤微生物、养分组成）调控，并会对地上营养级互作产生影响。本研究旨在探究土壤中的昆虫蜕壳是否会改变植物挥发物组分，以及其在实验室条件下对寄生蜂的吸引效应，并验证该吸引效应在野外是否同样存在。
我们以三种昆虫——黄粉虫（Tenebrio molitor）、家蟋蟀（Acheta domesticus）与亮斑扁角水虻（Hermetia illucens）——的蜕壳进行土壤改良，连续三年在野外探究该处理对被寄生的小菜蛾（Plutella xylostella）幼虫及甘蓝蚜（Brevicoryne brassicae）种群寄生率的影响。在实验室中，我们收集并分析了经土壤改良且被小菜蛾幼虫或甘蓝蚜侵染的植物的挥发物组分，并分别利用嗅觉仪评估了两种寄生蜂——菜蛾盘绒茧蜂（Diadegma semiclausum）与桃蚜茧蜂（Diaeretiella rapae）——对这些挥发物的趋性。
本研究表明，施加昆虫蜕壳的土壤可提升野外两种植食性昆虫的寄生率。土壤改良会改变植物挥发物多种组分的相对含量；施加家蟋蟀或黄粉虫蜕壳的土壤，可使嗅觉仪中两种寄生蜂的趋性显著增强。
施加昆虫蜕壳的土壤改良处理可改变植物挥发物组成，进而在实验室检测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。本研究结果凸显了地下过程（如昆虫蜕壳的分解）对地上以挥发物介导的多营养级互作的重要性。