The United States Environmental Protection Agency has approved the use of oxalic acid for use in honey bee colonies. According to information in the registration decision, “Due to the significant problems this parasite poses for honey bees, the EPA review of the application was conducted under a greatly expedited process.” You can read the full decision here, “Registration Decision for the New Active Ingredient Oxalic Acid.”
Contrary to the title, there is nothing new about oxalic acid for Varroa control. It is currently registered and widely used in Europe and Canada, and many U.S. beekeepers have been using it for years. Oxalic acid is readily available from hardware and paint stores where it is sold as “wood bleach.”
However, with the new regulation, its use will be legal and it will be labeled for use on colonies. The proposed two-page label can be seen here. It allows for the chemical to be administered in syrup, as a vapor, or as a spray.
Oxalic acid does not kill Varroa within capped cells and may, in fact, harm open larvae. As a result, oxalic acid treatments are most effective when brood rearing is at a low point. As with all miticides, the use of oxalic acid should be alternated with other preparations to reduce the chance of resistance.
In an upcoming post, I will share my system for using oxalic acid in a beehive.