D3194: Evaluation of Varroa destructor mite control options in Apis mellifera honey bee colonies established with queen cells

Varroa destructor mites are considered the leading cause of Apis mellifera honey bee colony losses in the U.S. and Canada. Varroa management currently relies heavily on chemical miticides, especially synthetics. However, a core tenet of Integrated Pest Management (IPM) is that physical, cultural, and biological controls should be used alongside chemical control. We investigated the effects of natural Varroa treatments (i.e., miticides based on naturally occurring compounds), combined with a widely used cultural control method (i.e., starting new colonies with queen cells), on Varroa mites. We started 177 new experimental colonies using queen cells – immature queens (cultural control). Experimental colonies either served as untreated controls or received one of several treatments (chemical control). We measured the Varroa infestation of adult bees the day of establishment and post-treatment, 75 days later. Samples from untreated control colonies had 5.9 times as many Varroa at the end of the trial as when the colonies were established. Varroa infestations in treated colonies either rose modestly, remained similar, or were reduced. We estimated the following treatment efficacies: Apivar® (81%); Amitraz E.C. (95%); Oxalic Acid Dribble (67%); Oxalic Acid Vapor (59%); Repeated Oxalic Acid Dribble (70%); and HopGuard 3® (93%). These results suggest that natural treatments based on oxalic acid and hops acids can rival the efficacy of amitraz-based (synthetic) treatments when strategically applied after installing queen cells in new colonies. This combination of cultural and chemical control provides an opportunity to rotate with natural miticides, reduce Varroa damage, and reduce colony losses from Varroa.