Essential oils againstVarroa destructor: a soft way to fight the parasitic mite ofApis mellifera

Essential oils (EOs) extracted from the aromatic plantsArtemisia annua,Artemisia verlotiorum,Cinnamomum verum, andCitrus reticulatawere investigated as repellents against the honey bees parasitic miteVarroa destructor. In laboratory tests, all EOs exceptC. reticulataexerted significant repellent activity against the mite after 24 h exposure.C. verumwas the most effective EO againstV. destructor(median effective concentration EC50=1.30 mu L L-1), and the least toxic against honey bees (EC50= 13.29 mu L L-1). Because of its high selectivity ratio (A. melliferaLD(50)/V. destructorEC(50)= 10.22),C. verumEO was then tested to control varroosis in colonies in field trials. The results of open field tests confirmed the efficacy observed in the laboratory. After one week of treatment, colonies treated with the EO showed a significant reduction ofV. destructorinfestation (about 65% at the dose of 25.0 mu L L-1) and no negative effects onA. mellifera. Overall,our experiment indicated thatC. verumEO could be used to effectively control varroosis in the hive with no side effects on the bee colonies.