Effectiveness of confectioner sugar dusting to knock down Varroa destructor from adult honey bees in laboratory trials

Abstract

Direct and air-assisted dusting of fine confectioner sugar (25-40 μm mean particle size) with and without pre-anesthesia of honey bees by CO2 were studied as a physical control method of Varroa destructor under laboratory conditions on samples of 78 bees (range 49-107). CO2 anesthesia alone had no effect, while sugar dusting resulted in significant mite knock down. CO2 anesthesia did not affect the effectiveness of sugar dusting, and mean mite fall over 2 days resulting from direct dusting with 5 g sugar and from air-assisted dusting with 0.5 g sugar per sample was 91% and 62%, respectively, and this difference was significant (P = 0.001). Ninety-nine percent of the mites in the sugar treatment fell within 18 h of treatment. As a possible side-effect of the dusting, the presence of sugar particles in the T2 spiracles and their tracheal ducts from treated honey bees was investigated under scanning electron microscope. No sugar particles were found in them.