This is a study that compared the mortality of phoretic mites based on different application methods. 

> A second trial in December 2013 treated 89 broodless colonies with 2.25 g OA via sublimation to confirm the previous results. Varroa mortality was 97.6% and 87 (98%) of the colonies survived until spring. This confirms that applying OA via sublimation
in broodless honey bee colonies in winter is a highly effective way of controlling V. destructor and causes no harm to
the colonies.

The study doesn't discuss the winter cluster but I would assume that colonies in the UK during December might be in cluster - maybe the UK folks on the list could verify that. 

>Our results from the second trial (97.7% varroa mortality with 2.25 g OA) confirmed the high mite kill that can
be achieved via sublimation.  Secondly, sublimation resulted in no harm to the bees, either at the time of
treatment or four months later in mid-spring. In fact, it actually resulted in stronger spring colonies.


Al Toufailia, H., Scandian, L., & Ratnieks, F. L. (2015). Towards integrated control of varroa: 2) comparing application methods and doses of oxalic acid on the mortality of phoretic Varroa destructor mites and their honey bee hosts. Journal of Apicultural Research, 54(2), 108-120.


http://dx.doi.org/10.1080/00218839.2015.1106777

http://www.imkerverband-sgap.ch/kalender/OxalsaeureVergleich_JApiResearch2015.pdf


Bill Hesbach
Cheshire CT

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