Temporal and spatial distributions of pathogens in managed Florida honey bee (Apis mellifera) colonies

Western honey bee (Apis mellifera) pathogens are a major concern for beekeepers and pose a significant threat to colony health. From January – December 2024, adult honey bees were sampled monthly by beekeepers in twenty counties distributed around Florida. Bees from each colony sample were analyzed using PCR and microscopy to determine the temporal and spatial distribution of the following honey bee pathogens: Ascosphaera apis (causative agent of chalkbrood), Crithidia mellificae, Melissococcus plutonius (causative agent of European foulbrood), Lotmaria passim, Nosema apis, and Nosema ceranae. In total, 721 samples were collected, of which 4.3% were positive for A. apis, 65.2% were positive for L. passim, 25.3% were positive for M. plutonius, 84.6% were positive for N. ceranae, and < 0.01% were positive for M. mellificae. Crithidia mellificae and N. apis were not detected in any of the samples. There were significant differences in the presence of L. passim, M. plutonius, and N. ceranae based on the time of year and location of the colony, with pathogens trending towards higher abundance in summer in the northern part of the state. In addition, the infection level of N. ceranae varied throughout the year and by colony location, with higher infection levels in the southern part of the state. Our results show which honey bee pathogens in Florida need further monitoring, and when and where they are more likely to impact honey bee colonies.