However, he did share data from a two (2) hive test that showed that the repeated application of oxalic acid vapor at two (2) week intervals successfully controlled mite levels and did not harm the hive in any way after 9 applications. Remember this was limited test with only two hives. Also, remember that oxalic acid vapor is not approved for use when honey supers are in place.
I would also like to report that beekeeper Jon’s hives are doing very well. Last year at this time he had lost ALL his hives. (See 1the 5 November 2017 blog article BIG MYSTERY). We had attributed that total loss due to trying to control mites via an oxalic acid/alcohol fogging method seen on the internet. This summer beekeeper Jon changed to oxalic acid vapor as his control method and has got past the crisis period with mostly strong hives. He has also seen low mite counts when periodically checking mite levels with the alcohol wash method. Starting with 12 packages in May and doing early June splits he was able to end up with 22 hives going into winter.
In mid-October I applied an oxalic acid vapor treatment to all my hives and winter nucs. This will be repeated the first week of November, weather permitting, and is my last planned treatment prior to the onset of winter. Remember that varroa mites are the main transmitters of viruses and the serratia marcescens sacarria bacteria, which is endemic in Wisconsin.
I also applied two (2) inch foam insulation around my winter nucs. I know what you are thinking; “he has repeatedly stated that winter wrapping is of doubtful value”. That’s still my position for full size hives, but for nucs, which start the winter with a much smaller cluster, I bent my rule to give the nucs a little help. This is my second attempt to overwinter nucs. My first attempt last winter was not successful. Last year's three (3) nucs succumbed in early January.
Four nucs gathered together for shared warmth and covered with 2" insulation
Presently all my hives and nucs are alive. The bees occasionally make an appearance outside the hives in the afternoon when temperatures exceed 50F. But for the most part they will be staying inside the hive for the next five months.
My next task for early November is to reposition the entrance reducers to the smallest entrance size (1 inch) and add mouse guards.
In late November I will be adding a 3 inch spacer beneath the inner cover to allow future addition of 2 ½ pound sugar discs as emergency food which some hives may utilize in late winter.