Many beekeepers decide to use organic acids such as lactic acid, oxalic acid or formic acid. These acids or their salts are found naturally in the metabolism of plants and animals, or directly in some varieties of honey. Organic acids are also used after the final honey harvest in the autumn and winter, and prevent critical amounts of parasites from remaining that would otherwise accumulate, above all, in the beeswax. A concentration in the wax to this effect would ultimately damage the honey too. In contrast to traditional treatment methods, the acids are not liposoluble, meaning that an accumulation in the wax is not possible. This method is recommended by some ministries and beekeeping institutes.
Formic acid is the only varroacide that can also be used for bee colonies with brood. The formic acid is introduced to the bee colony through evaporation. The Kalle Sponge Cloth is ideal for carrying out the evaporation.
For this type of treatment, a dry sponge cloth is placed onto a plate or a similar acid-resistant base. The formic acid required for treatment is then applied to this cloth using a syringe (60% ad us vet.). The sponge cloth is then placed without a base above the colony; for example, directly above the upper beam of the highest frame's mount. Since the steam from the formic acid is heavier than air, the steam falls thus reaching all bees. The sponge cloth should be removed from the colony one day after the last dose of treatment at the latest, otherwise the bees may cultivate or destroy this.
Treatment must be repeated at least once; however, mostly two or three times.