As many of you have heard, oxalic acid has been approved by the EPA for varroa mite control on honey bees. In the June issue of Bee Culture magazine, Jennifer Berry wrote an excellent article on the subject, which I suggest you read. See: http://www.beeculture.com/oxalic-acid-effective-easy-on-bees-but/.
Oxalic acid is an organic acid, a naturally occurring chemical found in plants and insects. It has been used for some time in both in Europe and in Canada as a varroa mite control. Since traces of oxalic acid are found naturally in honey, residues are not a concern. It is commonly sold for use as a bleach in woodworking, so is easily obtainable. The registration process for a pesticide, which is what oxalic acid is when used to control mites, is complicated. EPA approval has been given and oxalic acid should be legally available for use by beekeepers by late fall, but the paperwork is not yet complete. When finished, it will include registration in every state.
Though oxalic acid, like formic acid, is widely available, it appears that there will be a commercially available formulation like that for formic acid, and to use it legally, beekeepers will need to purchase this product. Brushy Mountain Bee Farm will be the distributor. (See: http://www.brushymountainbeefarm.com/). No other information about the product is available at this time, but I will keep you posted.
The registration for oxalic acid is for a liquid which can be used in that form or as a gas. In liquid form, it is mixed with sugar syrup and applied by “dribbling” a stream of the mixture between the frames of the hive, directly onto the bees. Package bees can be treated in the same way. Alternatively, it can be vaporized by the application of heat. Use the links below for more information on the possible treatment methods.
One very important caveat concerning oxalic acid as a miticide is that it only kills mites on bees, not those in the cells, and is most therefor most effective when used during periods with little or no brood in the hive. This is a serious limiting factor in its use.
Another note of caution is that the oxalic acid sold as wood bleach is close to 100% pure. For the safety of beekeepers as well as bees, the registered product is a 3% solution. Don’t be misled. Oxalic and formic acids, both “natural” products, are never-the-less both quite toxic in the wrong concentration. See: http://www.savogran.com/pdfs/Wood_Bleach_MS.pdf
For additional information, see the links below.
Bulletin from Dadant & sons concerning approval by the EPA of oxalic acid for varroa control:
An Investigation of Techniques for Using Oxalic Acid to Reduce Varroa Mite Populations in Honey Bee Colonies and Package Bees, PhD dissertation by Nicholas Aliano, University of Nebraska, 2008
Oxalic acid: A prospective tool for reducing Varroa mite populations in package bees, Nicholas Aliano, University of Nebraska, 2009 http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1186&context=entomologyfacpub
Oxalic Acid: Questions, Answers, and More Questions, Post by Randy Oliver