Honey bees are threatened by pathogenic organisms such as the Varroa mite (Varroa destructor) and the parasitic microsporidia Vairimorpha apis and Vairimorpha ceranae. Lithium chloride (LiCl) has been shown to be effective in controlling Varroa, while silver nanoparticles have been shown to be effective in controlling microsporidia. In this master's thesis, we investigated if application of LiCl and silver nitrate (AgNO₃) is safe for the Carniolan honey bee (Apis mellifera carnica). In a 10-day chronic oral test, we determined the impact on survival, feeding rate and behavioral changes in bees. We used concentrations of up to 1000 mg/L LiCl and up to 400 mg/L AgNO₃. LC₅₀ values were determined at 99.170 mg/L for LiCl and 218.241 mg/L for AgNO₃ after 10 days of exposure. For both substances, mortality depended on concentration and duration of exposure, showing a clear trend of increased mortality at higher concentrations. Both substances affected the feeding rate. Behavioral changes, such as reduced activity and uncoordinated movement, were more frequent at higher concentrations of both substances. Two-choice tests showed neither preference nor aversion to sucrose solutions with the addition of LiCl or AgNO₃. Due to the observed negative effects on survival, feeding, and behavior of honeybees, the use of LiCl and AgNO₃ in beekeeping requires caution. Before any practical application, further research would be necessary to evaluate long-term effects, determine safe concentration thresholds, and assess impacts on different developmental stages of honeybees.
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