Bee Health Guide
Recognising bee diseases and knowing effective control and prevention methods are sine qua non conditions for ensuring bee health and for good beekeeping practice. Diseases spread not only very rapidly within hives because of physical contact between worker bees and trophallaxis (the exchange of food between bees), but also between hives. Because bees can fly over long distances, rob neighbouring colonies, or drift into them, the risk that a large number of colonies and apiaries will be affected by a disease or an epizootic is significant. When one also considers the movement of hives by beekeepers and the high density of apiaries in Switzerland, the prevention of epizootics and diseases becomes even more important in bees than in other livestock animals, which can be quarantined more easily.
This guide complements the laws and technical directives relating to bee diseases. The table of contents is organised alphabetically. The guide is divided into the following categories: “Epizootics to be controlled: American foulbrood and European foulbrood”, “Epizootics to be monitored: acariosis and small hive beetle” and “Other bee diseases”.
Multiple pesticide exposure: combined effects and consequences for honey bee health
In agricultural environments, honey bees are typically exposed to mixtures of pesticides rather than single compounds. In addition to insecticides, fungicides and herbicides are frequently present. Conventional toxicological assessments often evaluate individual active ingredients, yet the document highlights that mixtures can produce synergistic effects, where combined toxicity exceeds the sum of individual impacts.
A critical mechanism involves the bees’ detoxification systems. Certain fungicides inhibit cytochrome P450 enzymes responsible for metabolising insecticides. When such fungicides are present, even sublethal insecticide doses can become significantly more toxic. This interaction is particularly relevant during crop flowering periods, when multiple treatments may overlap.
Beyond acute mortality, sublethal effects include impaired orientation, reduced learning ability, disrupted brood development and weakened immune function. At colony level, these impacts can reduce foraging efficiency and long-term productivity. Interactions with biological stressors such as Varroa destructor and viral infections may further exacerbate vulnerability.
The analysis emphasises that laboratory tests on single compounds do not fully reflect real-world exposure scenarios. In practice, bees encounter repeated low-dose exposure and potential accumulation of residues in wax and pollen. Chronic multi-compound stress challenges the bees’ detoxification capacity over extended periods.
From a beekeeping perspective, coordination with farmers regarding spraying schedules and flowering periods can mitigate risk. Apiary placement in relation to intensive agriculture is also relevant. Maintaining strong colonies through effective Varroa control and adequate nutrition enhances resilience against chemical stress.
In summary, pesticide risk to honey bees depends not only on the intrinsic toxicity of individual substances but also on their combinations, chronic exposure patterns and interactions with biological stressors. Realistic risk assessment must therefore incorporate mixture effects and colony-level context. :contentReference[oaicite:2]{index=2}
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