Honey can be contaminated by various natural and anthropogenic substances, posing a health risk to consumers. Pyrrolizidine alkaloids (PAs) are naturally toxic compounds many plant species produce to protect against herbivores. Honey may become contaminated if bees collect nectar and pollen from PA-producing plants. Clopyralid is the active ingredient in some herbicides, including Matrigon 72 SG, approved for weed control in oilseed rape in several countries. As a systemic substance, its application before flowering may contaminate nectar, pollen, and honey. In 2023, 30 Norwegian honey samples were tested for the content of PAs and 22 other honey samples for clopyralid. Pyrrolizidine alkaloids were detected in 20 per cent of the samples, but predominantly at low levels (<12 mu g kg(-1)). One sample contained a higher level (27.8 mu g kg(-1)). Clopyralid was detected at levels exceeding the EU Maximum Residue Level (MRL) at the time (0.05 mg kg(-1)) and the current EU MRL (2024) (0.15 mg kg(-1)) in seven of 22 honey samples, including five honey samples produced close to clopyralid treated oilseed rape fields, one honey sample collected next to unsprayed fields, and in one sample received from a beekeeper. It was later clarified that beehives in proximity to unsprayed cropping areas with honey with a high clopyralid content also were close to conventional clopyralid-treated oilseed rape fields. The results indicate that a more extensive survey would be appropriate to evaluate whether PAs and clopyralid are a common problem in Norwegian honeybee products.
Complex host-vector-virus interfaces can impose serious health challenges. Western honeybees have experienced high colony losses globally, mainly driven by the host-shifted, virus-vectoring ectoparasitic mites Varroa destructor and Tropilaelaps mercedesae. Host populations can survive mite infestations through natural selection, offering a long-term strategy for colony health. However, host-vector-virus coevolution requires local adaptations of this triad, which is poorly understood. We propose harnessing natural selection through a global approach focused on standardized monitoring of colony survival, mite infestation levels, and control of reproductives. Studying native and adapted mite hosts, host shifts, and comparing susceptible to surviving hosts will enhance understanding of this host-vector-virus system. This strategy promotes colony health in both managed and wild host populations and provides insights into other host-vector-virus interfaces.
Honey bee colonies can be infested by a range of pathogens, resulting in considerable morbidity and mortality. Detection and identification of pathogens in bee colonies is thus essential in apiculture, and various matrices are used for screening for pathogens within a colony, including hive debris, bees, and the combs. Previous investigations have explored using honey as a non-invasive sample material for detection of pathogen DNA, but have rarely compared the results with those from molecular analysis from other matrices. In this study, samples of bees, honey, and hive debris from beekeepers in Norway were investigated for several pathogens: Acarapis woodi, Crithidia mellificae, Lotmaria passim, Ascosphaera apis, Nosema apis and Nosema ceranae. For all sample types and all pathogens, pathogen-specific qPCR was used for detection, with microscopy methods also used for A. woodi and Nosema spp. Honey was the most difficult matrix to work with in the laboratory, and detection seemed to be lower than in hive debris or bees, depending on pathogen. While hive debris seems to be the optimal matrix for investigating honey bee colonies for Nosema spp. and A. apis, for L. passim bee samples provided the most positive results, and with lower Cq values. qPCR was significantly more sensitive for detecting Nosema than microscopy, and also provides the species information. None of our samples were positive for A. woodi or C. mellificae, but A. apis and Nosema spp. occur widely among apiaries in southern Norway, with N. apis being the predominant Nosema species.
