The nightmare before Christmas: first cases of thymol resistance in Varroa destructor
1Istituto Zooprofilattico Sperimentale del Lazio e della Toscana “M.Aleandri”, Unità Operativa di Apicoltura
2Università degli Studi di Milano, Dipartimento di Scienze Veterinarie e Sanità Pubblica
Thymol mechanism of action in Varroa destructor is basically neurological and is related to the interference with tyramine and octopamine receptors of the nervous system of the mite. The neurological receptors used by thymol are the same used by amitraz, against which notoriously Varroa destructor already showed documented resistance.
In our poster we report the results of 4 field trials realized in Italy in 2008 and in 2013, to verify the miticide efficacy of two commercial thymol-based veterinary products: Apiguard® and ApiLife Var®. To evaluate the acaricide efficacy we counted the number of mites fallen on the bottom trays provided with sticky boards, during the 28 days of products administration (Apiguard®: 14 days for each of the two trays; ApiLife Var®: 7 days for each of the 4 tablets), according to the label indications. We compared the amount of mite fall due to the treatments, with the amount of surviving mites counted for one week after the application, in brood absence obtained by caging the queen for 21 days, of a double dose (4 strips/hive) of Apistan® (tau-fluvalinate) associated to a single dose of trickled oxalic acid solution administered at a rate of 5 ml of solution for each intercomb occupied by bees.
In the 2008 field trials, the mean acaricide efficacy we obtained with Apiguard® was of 72.2%±17.7, while in 2013 we reached an acaricide efficacy with Apiguard® ranging from 58.0%±11.3 to 61.5%±10.7. ApiLife Var®, similarly, reached a miticide efficacy of 30,1%±5.0. In our poster, results of the recorded temperatures will be detailed.
Data obtained from the field trials above mentioned could represent the first signs of thymol resistance in Varroa.