A young bee attacked by Varroa mites.
Photo: © University of Hohenheim, Bettina Ziegelmann

Researchers discover drug for treating Varroa mites

Hope for bee-keepers all over the world: for the first time, researchers at the University of Hohenheim have discovered a drug that can be administered through the feed, with the potential for freeing attacked bee stocks from the feared Varroa mite with little labour involved.

The Varroa mite is one of the most dangerous enemies of bees in the world: in just one to three years, it can completely eradicate a bee population. To date, bee-keepers have had to treat attacked bee stocks with aggressive organic acids or chemically produced mite control agents which involve resistance problems and residues. The promising substance now developed is lithium chloride, which is easily available.

After 25 years of research, a team at the University of Hohenheim in Stuttgart, Germany, have succeeded in developing a drug which can free bee stocks from the globally dangerous Varroa mite.

Lithium chloride is a cheap substance and easy to use against the dangerous mite; as far as researchers currently know it has no dangerous side effects for bees, bee-keepers or consumers, and is freely available in nature. It gives the research team an active substance for a drug which is easy to obtain and administer. There are no signs to date of any accumulation in the honey.

Dr Peter Rosenkranz, Director of the Land Institute of Apiology, explains the advantages of the active substance. “You can feed bees lithium chloride dissolved in sugar water. In our trials, even minimal amounts of the solution have been sufficient to kill off the mites infesting the bees – without any side effects for the bees.”

Lithium’s availability is another advantage. World reserves of the light metal are estimated at over 40 million tons, and lithium chloride salt is found in brine, salt lakes and mineral springs. The salt is easily soluble in water and currently used as a drying agent, in de-icing solutions and for other purposes. It has been used as an antidepressant in human medicine since the mid-20th century.

However, before it can be brought to the market as a drug for bees, further tests are needed to determine the optimal dosage, rule out side effects for bees and users and exclude the risk of residues. The Hohenheim team reports that discussions are currently underway with companies interested in continuing the development.


Bettina Ziegelmann et al.: Lithium chloride effectively kills the honey bee parasite Varroa destructor by a systemic mode of action , Scientific Reports 8, Article number: 683 (2018), doi:10.1038/s41598-017-19137-5

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