Assessing low-dose lithium salts for Varroa mite (Varroa destructor) management in honeybees (Apis mellifera): field efficacy and health implications.

The pollination of wild plants and crops increasingly depends on insects, with the European honeybee (Apis mellifera) recognized as the most vital pollinator. A significant factor contributing to colony collapse disorder is the infestation of ectoparasitic varroa mites (Varroa destructor). As a result, there is considerable interest in developing new acaricides and optimizing doses to effectively manage these mites. This study aimed to evaluate the effects of low doses (0.125, 0.5, and 2 mM) of lithium salts (lithium acetate, lithium chloride, and lithium citrate) against varroa mites in honeybee colonies under field conditions. This study also assessed the effects of lithium salts on honeybee workers, particularly under conditions of food deprivation and low or high temperature stresses. Our findings indicated that colonies treated with 2 mM lithium chloride or 0.5 mM lithium citrate exhibited either 100% or 87.5% reduction of the initial mite infestation rates, respectively. Furthermore, the total mortality of bees in hives treated with lithium chloride did not differ significantly from those treated with oxalic acid. Additionally, the brood area of bee colonies receiving lithium salts was comparable to that of colonies treated with oxalic acid and fluvalinate, and significantly larger than that of untreated colonies. An in vitro study further demonstrated that honeybees receiving lithium salts displayed greater stress tolerance compared to those treated with fluvalinate under conditions of food deprivation, cold, and heat stress. This study demonstrated that low doses of lithium chloride and lithium citrate could effectively control varroa mite infestations in field conditions without significant negative impacts on bee brood development or stress tolerance.