THE INFLUENCE OF FORMIC ACID, OXALIC ACID AND ESSENTIAL OILS ON THE FREE ACIDITY IN HONEY

The aim of the study was to monitor the changes in the free acidity of honey after administration of three anti-varrotic treatments with the use of formic acid (FA), oxalic acid (OA) and essential oils as the active substances in commercial preparation. To the first experimental group, 60 % FA was administered by vaporization using the vaporizer Nassenheider Professional® (group F). OA was administered by the contact in the form of 26.8 % (w/w) glycerine solution of OA on special workshop towels (group O). Essential oils were administered in the form of the commercial product Bisanar® (group B). The control group received no treatment during the experiment. Although the acidity of the honey in the B group during the experiment did not show significant difference compared to the control group (p = 0.769) and only a slight difference was determined in the O group (p = 0.416), the F group showed significant increase of the values compared to the control group (p = 0.015). The average value of free acidity in honey of this experimental group did not decrease notably under the legislative limit after two weeks following removing the treatment from the hive. Free acidity in the F group reached the value of 57.50 ± 25.19 mEq/kg (milliequivalents per kg) at the end of the experiment. Treatments by OA and Bisanar® are more suitable to supress varroosis during the summer without significant increase of free acidity in honey.