High Sensitivity of Tropilaelaps mercedesae to Lithium Chloride: A Novel Acaricidal Candidate for Honey Bee Health

The escalating threat of the ectoparasitic mite Tropilaelaps mercedesae requires novel control strategies for honey bee (Apis mellifera) health4. In this study, we provide the first evidence of the acaricidal efficacy of lithium chloride (LiCl) against this emerging parasite. Ex situ contact bioassays quantified the dose-response relationship, revealing a 12-hour LC50 of 45.9 mM. These results indicate that T. mercedesae is intrinsically more than 3.5 times more sensitive to LiCl than the widespread Varroa destructor. We translated these findings to field conditions in a pilot trickling trial on infested A. m. ligustica colonies. Repeated administration of 500 mM lithiated sugar syrup induced characteristic tremors and a sharp increase in mite fall, confirming that the acaricidal effect manifests in situ even in the presence of brood. Our findings identify lithium as a highly effective, naturally occurring candidate for Tropilaelaps management. This warrants larger-scale trials to refine application protocols and evaluate long-term colony safety for sustainable apiculture.