Micro‐ and Macroparasites Associated With South American Bumblebees ( Bombus spp.) (Hymenoptera: Apidae)

ABSTRACT Bumblebees ( Bombus spp.) are essential pollinators of wild and cultivated plants across South America. Of the 26 species recorded on the continent, two are introduced—the Buff‐tailed bumblebee ( Bombus terrestris L.) and the large garden bumblebee ( Bombus ruderatus Fabricius). Native bumblebees are subject to multiple pressures—habitat loss, agricultural intensification and competition with introduced congeners—but pathogens and parasites represent an additional, under‐recognised threat. This review synthesises the available evidence on microparasites/pathogens (viruses, bacteria, fungi, microsporidia, protists) and macroparasites (nematodes, mites), including phoretic mites and parasitoids, affecting bumblebees in South America. Records span from 1972 to 2025, encompassing both published literature and non‐digitised sources from regional libraries and entomological collections, as well as diagnostic and molecular studies. Detected agents include widely distributed taxa such as Nosema ceranae , Apicystis bombi , Crithidia bombi and deformed wing virus—several shared with the Western honey bee ( Apis mellifera L.)—suggesting potential interspecific transmission. Some pathogens appear to be regionally restricted; for example, the microsporidium Tubulinosema pampeana has been reported only associated with Bombus pauloensis Friese from the Pampas region. Knowledge is geographically and taxonomically biased: most data originate from Argentina and Chile, and only a minority of bumble bee species have been screened. Prevalence estimates vary markedly, and the demographic and fitness consequences for native populations remain unknown. Of particular concern is the role of introduced bumble bees as pathogen reservoirs and/or dispersal agents that may exacerbate declines in native congeners, including the endangered Patagonian bumblebee (Bombus dahlbomii Guérin‐Méneville). We identify priority research needs—expanded geographic sampling, standardised molecular diagnostics, experimental infection assays and coordinated regional research programmes—to improve understanding of pathogen dynamics and to inform conservation and management strategies for South American bumble bees.