Developing sustainable parasitic mite management strategies for beekeepers

Abstract

The Western honey bee (Apis mellifera) is an important pollinator worldwide, contributing billions annually to the global economy through pollination services. Honey bees face a variety of different stressors that can cause colony losses. Colony losses have increased in recent decades and one of the leading causes of them in the Northern hemisphere is the parasitic Varroa destructor mite. The mite damages honey bee colonies by feeding on adult and developing honey bees while also vectoring various viruses. In the United States, this parasite is primarily controlled by synthetic acaricides; however, continued reliance on these synthetic acaricides, most recently amitraz, has led to increases in resistant V. destructor mites, thereby limiting potential treatment options. Compounding the issue of invasive parasitic mites for beekeepers is the appearance of a new threat, Tropilaelaps mercedesae. While still primarily limited to its native range in Southeastern Asia and Australasia, T. mercedesae has recently been confirmed in parts of Western Asia and Eastern Europe, regions previously thought to be unsuitable for the mite. Tropilaelaps mercedesae feeds on developing honey bees, like V. destructor, but not adults and can cause colony failures. In this dissertation, I conducted experiments exploring sustainable beekeeping practices while looking to fill knowledge gaps relating to V. destructor and T. mercedesae. I conducted two experiments that evaluated the effectiveness of fall V. destructor treatments in the Southeastern U.S., a critical time to manage V. destructor infestations. From these two experiments, I identified viable alternative treatments to amitraz and demonstrated that continuous treatment with this synthetic chemical increases the amitraz resistance allele frequency for V. destructor, albeit briefly. For T. mercedesae, I contributed to mapping the current global range of the mite and documented a potential dispersal method for the mite on adult honey bees exiting the colony. This suggests that the mite could disperse through honey bee drifting or robbing behaviors. Lastly, I showed that T. mercedesae could be controlled in, although not eradicated from, colonies using a combination of a cultural and chemical control method. Overall, my work provides important information regarding sustainable mite management strategies to help beekeepers understand and control both V. destructor and T. mercedesae. Ultimately, my findings will help to limit future colony losses.