The mite Varroa destructor is an obligatory ectoparasite of the honey bee (Apis mellifera) and is one of the major threats to apiculture worldwide, not only because of its direct effect on the honey bee, but also because of its role as a vector for various bee viruses. The devastating impact of the mite encourages researchers and beekeepers towards a better understanding and controlling of this mite. Lithium chloride, used as a solvent for RNAi in studies of the targeted exclusion of vital parasite genes, is an effective substance for the suppression of the varroa mites. We were interested in whether the concentration of lithium in tissue, brood and honey bee crops would increase after the treatment of honey bees with sugar solution containing 25 mM LiCl. We found that following per os feeding with 10,6 μg LiCl, 6,5 mg/kg to 40,1 mg/kg Li accumulated in worker bees body parts and had a negative impact on their survival over a period of seven days after the start of a treatment. The treatment with the test solution increased the mortality of varroa, resulting in a decrease in the infestation with the varroa mite in the honey bee family. LiCl also increased bee mortality five days after the start of three-day treatment with test solution. After ad libitum treatment with 25 mM test solution, the larvae accumulated on average 39,5 ± 2,53 mg/kg, while in honey there was 0,879 ± 0,356 mg/L and in pollen 30,75 ± 12,66 mg/kg (mean ± standard deviation) of lithium. Due to its negative impact on honey bee survival and high accumulation in tissue and crop, LiCl alone seems to be unsuitable for the control of varroa.
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