Environmental DNA Methods for Detection of Varroa destructor in Honey Bee (Apis mellifera) Hives

Abstract

The parasitic mite, Varroa destructor, is a worldwide problem for honey bees (Apis mellifera). The recent spread of this pest to Australia, which was one of the few varroa-free honey bee populations remaining, highlights the importance of effective biosecurity methods for managing incursions. Detection of varroa mite environmental DNA (eDNA) could be a valuable complementary tool to increase the sensitivity and cost-effectiveness of varroa surveillance as it spreads to new areas. Using a newly developed V. destructor quantitative PCR assay, we deployed eDNA testing on honey bee hives in New Zealand and Australia with a range of mite infestation levels. The detection sensitivity of eDNA methods using honey and hive surface swabs was comparable with a conventional alcohol wash method used by beekeepers, with the advantage of not harming bees. However, we observed greater variability in eDNA detection, particularly for hive entrance swabs, when estimated mite infestation levels were below 1%. Using varroa-free hives introduced from the Chatham Islands to Wellington, New Zealand, we were also able to show that V. destructor eDNA was detectable during the initial invasion of hives. Our data highlight the potential for incorporating eDNA methods into Australia's biosecurity surveillance programs to help limit the spread of varroa mites to new areas and detect future incursions.