Improving honey bee colony health - coordinated control of the ectoparasitic mite, Varroa destructor

Honey bee colonies in the UK are parasitized by Varroa destructor, an ectoparasitic mite, which acts as a vector for all strains of deformed wing virus (DWV). The combined infestation of mites and infections with the transmitted viruses are responsible for 15-25% colony losses across the UK per annum and no regulated control treatments are currently in place. However, some miticides provide very effective treatment and controlled usage would lead to significant decreases in Varroa levels and consequently lower virus levels and healthier colonies.
The primary objective of this study is to use coordinated treatment of Varroa infestations of bee colonies in a geographically isolated environment to show improvements in honey bee health. This will be achieved through the coordinated treatment of colonies on the island of Arran off the west coast of Scotland and will be measured by examining the population diversity and levels of deformed wing virus (DWV), a pathogen transmitted by the Varroa mite, present in the colonies. The objective of this study is to test whether these coordinated treatment methods can improve colony health and that the introduction of this practice to beekeepers across a wide geographic area should result in long term improvements in bee health on a large scale. We will sample colonies from each site on Arran pre- and post-treatment and identify the virus levels and diversity in the population. The testing will be repeated over three years to study the long-term effect of the treatments. This study will attempt to use coordinated treatments on a landscape level to reverse the effects of Varroa introduction, such as those observed in Hawaii (Martin et al. 2012), and show that coordinated treatments of miticides can drastically reduce Varroa infestation and potentially improve colony health. We will examine the levels of DWV in the bees collected during field sampling on Arran using high throughput sequencing to identify the diversity of the viral population and determine whether the presence of a dominant viral genotype pre-treatment can be shifted to a mixed population post-treatment.
As field studies on a landscape scale can be difficult to control and monitor, a local study will also be performed. The effects of Varroa infestation (through drifting from adjacent hives) on Varroa-free colonies and the effect of miticide treatment on Varroa-infested colonies will be studied in a "colony-exchange" experiment with the Bowman group (University of Aberdeen). The objective of this study will be to determine how rapidly colonies which have previously been Varroa-free succumb to Varroa infestation and subsequently an increase in viral levels and decreased diversity is observed, as with the colonies observed in Hawaii (Martin et al. 2012). We will also attempt to "rescue" Varroa infested colonies and observe if the viral population reverts to low level, high diversity based on consistent miticide treatment. The extent to which the viral population changes in the colonies depending on Varroa infestation and treatment will be examined by testing adults, pupae and larvae at frequent intervals and measuring the DWV population diversity using next generation sequencing methods. This will give us a clear idea of the effect of miticide treatment on the virus population and will emphasize the impact of coordinated Varroa control processes such as the one we will perform on Arran.A final objective of this project will be to examine the residues left of an oxalic acid-based miticide treatment for Varroa infested colonies and whether this has a long term accumulative effect on the comb and honey in the colony which may impact the practical use of this treatment for beekeepers. Oxalic acid is an effective treatment chemical, but the long-term effect of the miticide on comb and honey has not been fully investigated. Here we propose using HPLC methodology to investigate the comb chemistry and determine whether the residues are