Mating disruption of the honeybee mite Varroa destructor under laboratory and field conditions

Abstract

Mating in the mite Varroa destructor, an ectoparasite of the honeybee, takes place within the sealed brood cell of its host and is triggered by a female sex pheromone consisting of three fatty acids and their respective ethyl esters. In a laboratory bioassay, we observed interactions among offspring of a Varroa female at 11 days after host cell capping in the absence and in the presence of the sex pheromone and clearly demonstrated that male mites were not able to distinguish between receptive daughters and either older or immature and unreceptive females when exposed to the pheromone. In addition, mating attempts in the presence of the pheromone with otherwise receptive females were clearly of shorter duration and males often failed to select a receptive female. In order to evaluate the effect of pheromone exposure on successful copulations and the number of spermatozoa transferred under field conditions, we sprayed one of the pheromone components, oleic acid, on an empty brood comb before host egg-laying and Varroa infestation and counted the spermatozoa of daughter mites taken from this comb. We could show that the number of spermatozoa was indeed reduced, and 20 % of females lacked spermatozoa. Our results open up new possibilities and represent a promising step toward biological control of Varroa mites in beehives.