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Back to the Basics

Five consecutive years of data collection from the Bee Informed Partnership shows that treating with a known Varroa Mite treatment increases the survival rate of your colony. Beekeepers that treated for Varroa in 2014 lost far fewer, 26.8%, than those who did not. This is the fifth year this correlation has been documented. It would be irrational not to treat your hive this year.

A treatment that has grown in popularity recently is Oxalic Acid. Since the approval by the EPA and USDA (full article at: http://www.regulations.gov/index.jsp#!documentDetail;D=EPA-HQ-OPP-2015-0043-0119) Oxalic is undergoing registration for use in each state. Check to see if your state is registered.

Oxalic Acid is not a new treatment for varroa as it has been legal to use on honey bees in Europe and Canada due to its efficacy and low risk of hive contamination. It is a naturally occurring acid found in a number of plants and also occurs in honey.

The most effective treatment time is generally when colonies have no sealed brood.


  • This opportunity naturally occurs with brood breaks in late fall through winter. Treatments may be applied when temperatures are above 32 degrees Fahrenheit.

  • Brood break may be induced by caging the queen for 14 days. This gives you a two day window six days after the queen is released. Information provided by Randy Oliver: http://scientificbeekeeping.com/oxalic-dribble-tips/

  • Applying the treatment to splits, swarms, or packages after they have been transferred to a hive. Do not apply immediately after the transfer, rather, allow the queen to lay eggs first. The immediate treatment may overwhelm the colony and result in the colony absconding.

  • Oxalic Acid is not an effective treatment when capped brood is present in the hive. Oxalic does not penetrate capped brood and when the brood emerges, so will a new generation of varroa.

    The effectiveness of Oxalic Acid treatments used in solution can be in excess of 95%, lower if using vapor method. Honey Bees have a low tolerance to oxalic acid, there¬fore, only one application should be made. Here are two application methods to use:

    SOLUTION METHOD:
    NOTE: To completely dissolve Oxalic Acid Dihydrate, use warm syrup.
    Dissolve 35 g of Oxalic Acid Dihydrate in 1 liter of 1:1 sugar: water (weight:volume). Smoke bees down from the top bars. With a syringe or an applicator, trickle 5 ml of this solution directly onto the bees in each occupied bee space in each brood box. The maximum dose is 50 ml per colony whether bees are in nucs, single, or multiple brood chambers.

    Under certain unfavorable conditions (e.g., weak colonies, unfavorable overwintering conditions), this application method may cause some bee mortality or overwintering bee loss.

    VAPORIZER METHOD:
    Apply only to outdoor colonies with a restricted lower hive entrance. Seal all upper hive entrances and cracks with tape to avoid escape of Oxalic Acid vapor. Smoke bees up from the bottom board, Place 1.0 g Oxalic Acid Dihydrate powder into vaporizer. Follow the vaporizer manufacturer’s directions for use. Insert the vaporizer apparatus through the bottom entrance. Apply heat until all Oxalic Acid has sublimated.

    It is recommended that you assess your mite levels by performing a mite count before any treatment is applied to the hive. With this information you will be able to determine if your treatment was effective by checking mite levels upon completion of treatment. Mites can develop a resistance to certain treatments; therefore, a different treatment is required if mite levels remain the same or increase.