The Varroa destructor mite causes severe losses of Apis mellifera colonies, requiring recurring treatments. One such treatment is oxalic acid (OA), considered ecological. However, it is unclear whether OA affects the honey bee gut microbiota or other hive-associated microbiotas. Herein, we studied the effect of three OA treatments (trickling at 2.1% or 4.2%, and sublimation through Varrox®) upon microbial communities associated with workers’ gut, hive bee bread and pupae, sampled from conventionally or ecologically managed colonies under different anthropization levels (located in urban, rural or mountainous landscapes). We hypothesized that treatment with OA would impact the diversity and composition of bacteria and/or eukaryotic communities, and that the effect would be dose-dependent and specific to the beehive niche. Results showed that the microbiomes of apiaries under different anthropization levels and management strategies differed prior to OA application. Neither the bacterial nor the fungal communities of bee bread and pupae shifted due to OA treatment. Independent of the dosage and the application method (trickling or sublimation), OA induced slight compositional changes in the bacterial profiles of honeybee guts. Those changes were stronger the higher the anthropization (in colonies from urban areas under conventional management). OA treatment reduced the relative abundance of several pathogens, such as Nosema ceranae, and decreased the overall bacterial diversity down to values found in less anthropized colonies. Thus, our results suggest that, aside from managing Varroa infestations, OA could have beneficial effects for stressed colonies while not impairing honey bee resilience from a microbial point of view.

瓦螨会导致意大利蜜蜂菌落严重损失，需要反复治疗。其中一种处理方法是草酸（OA），被认为是生态的。然而，尚不清楚 OA 是否影响蜜蜂肠道微生物群或其他蜂巢相关微生物群。在此，我们研究了三种 OA 处理（滴加 2.1% 或 4.2%，并通过 Varrox® 升华）对与工蜂肠道、蜂巢蜜蜂面包和蛹相关的微生物群落的影响，这些微生物群取自不同人类化下的常规或生态管理的菌落水平（位于城市、乡村或山区景观）。我们假设 OA 治疗会影响细菌和/或真核生物群落的多样性和组成，并且这种影响将是剂量依赖性的并且特定于蜂巢生态位。结果表明，在应用 OA 之前，不同人类化水平和管理策略下养蜂场的微生物组存在差异。蜂面包和蜂蛹的细菌群落和真菌群落均未因 OA 处理而发生变化。与剂量和应用方法（滴流或升华）无关，OA 会引起蜜蜂肠道细菌谱的轻微组成变化。人类化程度越高（在传统管理下来自城市地区的殖民地），这些变化就越强烈。 OA处理降低了几种病原体的相对丰度，例如蜜蜂微孢子虫，并将总体细菌多样性降低到人类化程度较低的菌落中发现的值。因此，我们的结果表明，除了控制瓦螨侵扰之外，OA 还可以对受压力的蜂群产生有益的影响，同时从微生物的角度来看不会损害蜜蜂的恢复能力。