As you know varroa mites cause some of the most difficult challenges for bees and beekeepers. No matter what methods you choose to deal with mites they all have some kind of drawback and/or limitation. Some don’t work when it’s too cool others are dangerous to bees if it’s too hot, others aren’t effective if brood is present in the hive – etc. All of them are extra work and expense. So anytime a promising new method of treatment becomes available it is worth our time to look into it.
As you may know, Oxalic acid was made legal by EPA regulations as a treatment for varroa mites on honey bees about a year ago. This is not to say that using any old oxalic acid in any old way is now completely OK – technically any EPA-regulated substance must be used according to the label directions. So first of all the OA you use is supposed to be labeled for treating mites, and you would have to follow the label directions to be in complete compliance with the law. What I am about to describe would potentially be an off-label use at this time. But it is still worth learning about.
In the past Oxalic acid (an organic acid which naturally occurs in small concentrations in many foods) has usually been applied either in a liquid form (the so-called dribble or trickle method) or as a vapor by using a special piece of equipment to heat it up. Both of these methods have similar advantages and disadvantages – if done correctly they are both easy on the bees, not temperature dependant, and fairly effective. The big disadvantage to them is that they don’t kill mites that are inside of capped brood – That is a big limitation. Because of this limitation, OA treatments have only really been useful on hives which have little or no brood at the time of treatment.
Randy Oliver – http://scientificbeekeeping.com/ – reputable author and honey bee researcher. Has been experimenting with a simple way to apply oxalic acid in an easy to make time release form. Basically, he mixes oxalic acid with glycerin (a food safe substance) and saturates paper towels with the mixture. It takes the bees about 30 days to remove the treated paper towels from the hive – resulting in an effective time extended treatment which does kill mites inside of capped brood. You really should read the entire article for the complete info.
I first read about this work by Randy Oliver in this article on HoneyBeeSuite – which also contains good information on making oxalic acid – glycerin sheets.