Endosymbionts living within insect cells can modify host fitness and could provide new tools for pest control. The endosymbiont Rickettsiella viridis has been transferred experimentally into the green peach aphid, Myzus persicae, a globally important agricultural pest. This Rickettsiella spreads via vertical and horizontal transmission and induces host fitness costs which could potentially suppress pest populations. Endosymbiont prevalence can fluctuate in natural populations, and it is important to identify factors that contribute to their spread or loss. Here, we explore the effects of Rickettsiella infection when aphids are reared on eight different host plants or exposed to thermal, starvation and desiccation stresses. Rickettsiella infection reduced M. persicae fecundity and longevity across all host plants, but the magnitude of costs varied among host plants and generations. Rickettsiella was horizontally transmitted and spread in caged populations at initial ratios of 1:2 Rickettsiella (+): Rickettsiella (−) on all host plants, but with limited long-term persistence under cycling 20–30 °C. We also identified temperature-dependent costs of Rickettsiella infection on heat knockdown time, chill coma recovery, and starvation tolerance. Finally, we present evidence that Rickettsiella infection reduces host activity levels under heat stress. Our results suggest that Rickettsiella infections induce a variety of deleterious effects but with complex environment-dependent interactions. This work helps understand ecological conditions that enhance or limit the spread of these endosymbionts in aphid populations.

生活在昆虫细胞内的内共生体可以改变宿主的适应性，并可以为害虫防治提供新的工具。内共生立克次体（Rickettsiella viridis）已通过实验转移到绿桃蚜（Myzus persicae）中，这是一种全球重要的农业害虫。这种立克次体通过垂直和水平传播传播，并引起宿主健康成本，这可能会抑制害虫种群。内共生体的流行率在自然群体中可能会波动，因此确定导致其传播或消失的因素非常重要。在这里，我们探讨了当蚜虫在八种不同的寄主植物上饲养或暴露于热、饥饿和干燥胁迫时，立克次体感染的影响。立克次氏菌感染降低了所有寄主植物的桃支原体繁殖力和寿命，但成本的大小因寄主植物和世代而异。立克次氏菌在所有寄主植物上以 1:2立克次氏菌(+):立克次氏菌(−) 的初始比例在笼养种群中水平传播和传播，但在 20-30 °C 循环下的长期持久性有限。我们还确定了立克次体感染对热抑制时间、冷昏迷恢复和饥饿耐受性的温度依赖性成本。最后，我们提出证据表明立克次氏菌感染会降低热应激下宿主的活动水平。我们的结果表明，立克次氏菌感染会引起多种有害影响，但具有复杂的环境依赖性相互作用。这项工作有助于了解增强或限制这些内共生体在蚜虫种群中传播的生态条件。