Prevalence of pathogens in abnormal honey bees in South Korea, 2020-2023

South Korea's beekeeping industry has been facing a major crisis due to colony collapse disorder (CCD), manifesting since the winter of 2021. CCD in South Korea is presumed to be caused by a combination of factors, including an abnormal climate, pesticide use, declining source plants, and increased honey bee diseases. We examined the prevalence of 12 major honey bee (Apis mellifera) pathogens by sampling 3,707 colonies with abnormal behavior and suspected pathogen infections from 1,378 apiaries nationwide between 2020 and 2023. Black queen cell virus (BQCV), deformed wing virus (DWV), Israeli acute paralysis virus (IAPV), and Vairimorpha (Nosema) ceranae had the highest infection rates among honey bees in South Korea. BQCV had the highest infection rate (83.3% in 2023) and was highly prevalent throughout the year, regardless of the season. DWV (48.7%) and IAPV (41.3%) had the highest infection rates in October-December, corresponding to the winter season. Among the 12 honey bee pathogens, acute bee paralysis virus and Kashmir bee virus were rarely detected; the remaining 10 honey bee pathogens were detected throughout the year. The differences in honey bee pathogen prevalence among regions were not significant. We suggest that South Korean honey bees are highly exposed to viral pathogens, possibly resulting in the loss of unhealthy honey bees during the winter. Our study is expected to help identify trends in the occurrence of honey bee pathogens in South Korea and predict outbreaks to prepare a prevention system and appropriate control measures for honey bee pathogens.