Serumwerk Bernburg brand Oxalsäure Bernburg Solution (oxalic acid dihydrate) is used to treat Varroosis in honeybees. It is an effective treatment against the Varroa mite, a parasite that can significantly harm bee colonies. Typically used as a 3.5% sugar solution or a 3.0% spray solution, particularly during the brood-free period in late autumn. An EU Authorised product