In this video I explain the method that I use to treat my bee colonies for varroa mites in the Fall using formic acid in order to considerably reduce the varroa population ahead of winter.
You have to treat thoroughly the generation that will then grow the winter generation. Otherwise the winter gen will be weak and will not survive. So treat around aug1st 2-3 treatments and Then again after there is no more capped larvae. Good luck
how can this be very effective? Formic acid is heavier than air, to cover complete hive that towel should be on the top bar in the upper box , but at 48 % formic acid concentration.
That is true but somehow I still get a good mite kill rate with this method. Another option is to put the shop towel with the formic acid into a ziploc bag that has holes or slits in it and to deposit the bag on the top of the brood box. This is what I do for the hives that do not have a screened bottom board. I'll try to make a video about this method next time but you will find some on youtube if you search.
I would be hesitant to treat a weak hive this small unless you know that you have a mite problem. If it was me and I had to treat I would use about half a dose, or 15ml.
Tony Jenkins If used properly and when the outdoor temperature is not too hot there should be very minimal impact on the bees. Follow the instructions on the label.