Plant essential oils as potential control agents of varroatosis

Beekeeping has always been vulnerable to various sanitary drawbacks. The mite Varroa destructor (Mesostigmata: Varroidae), an obligated ectoparasite of honeybees, has been in recent times one of the major problems leading not only to economical losses but also to ecological problems related to the role of honeybees as the most important pollinators on Earth. Varroatosis has been treated by methods that include special practices of beekeeping, physical removal, and the use of synthetic acaricides. None of these methods have, however, rendered complete protection, and there is clear evidence for the evolution of resistance to conventional acaricides. Consequently, the need for alternative control means has prompted the onset of several prospecting programs on botanicals with anti-varroa potential. Among these, essential oils appear as good candidates for safer control. In this review, we provide a concise compilation of the information generated in the last years on essential oils with anti-varroa activity. Future developments in this area demand standardization of bioassay protocols (either in the laboratory for primary screening or in hives), a detailed chemical characterization of the essential oils tested, and comprehensive studies on application methods.