Updated nationwide monitoring of the main pests and pathogens affecting honey bees in Uruguay

Over the last decades, reports of high honey bee colony losses have raised concerns. In Uruguay, annual losses reach 30% every year, with infection by pests and pathogens being one of their main causes. In 2011, our group conducted a nationwide survey of major honey bee pathogens. In 2021, we performed a new one, evaluating the presence, prevalence, and distribution of pathogens, and whether the bees sampled were Africanized or European. We sampled honey bees from 100 colonies across the country during autumn/winter and evaluated the presence of Varroa destructor, Nosema spp., RNA viruses and Lotmaria passim using standard methodologies (microscopy, PCR, RT-qPCR). We also analyzed the genetic lineages of the honey bees. Nosema ceranae was the most prevalent (63%), while N. apis remained undetected. Varroa destructor was also highly prevalent (62%). In 2011, most beekeepers used synthetic acaricides to control the mite; ten years later, we observed a shift toward organic acaricides (i.e., oxalic acid). Lotmaria passim also showed high prevalence (60%), followed by DWV (31%), SBV (27%), CBPV (25%), BQCV (22%), and ABPV (6%). As in 2011, most colonies were Africanized (62.5%). These showed lower N. ceranae infection levels compared to European ones. This nationwide survey provides crucial insights into the prevalence and distribution of honey bee pests and pathogens. It highlights the importance of monitoring and the implementation of management strategies specifically adapted to local conditions to preserve colony health and ensure the sustainability of beekeeping.