Varroa destructor is an invasive parasitic lice, which is a serious threat to beekeeping throughout the world. There are many preparations for treating Varroa destructor on the market with various ingredients, but they have many disadvantages (residue of the active substance, and / or excipients in the final products of the bees, increased resistance of mites). Methanoic acid is an acid of natural origin naturally present in honey and is effective in controlling Varroa destructor. The main difficulty in preparing the pharmaceutical form with methanoic acid is its corrosiveness and high volatility (uneven evaporation, environmental impact on evaporation). Methylcellulose has proved to be the most suitable polimer for preparing gel. With methanoic acid, the gel has a suitable viscosity and consistency, but unfortunately the viscosity of the gel decreases with time due to depolymerization. Addition of glycerol and increase of methylcellulose content to 10% yielded a gel whose viscosity was suitable andpersistent for a long time. The evaporation test showed that the acid from the gel evaporated too quickly in comparison with the gel MAQS®.
The extent of depolymerisation and reduction of viscosity was lower in the case of recipes that did not contain purified water and its share was replaced by glycerol. A gel with a polymer concentration of 2.5% and 50% methanoic acid had appropriate physical properties and remained stable even after one month of observation. Determination of the evaporation rate of the acid showed a steady evaporation in the first week, then the binding of the water from the air occured, whereby evaporation of the acid was slowed down and the mass of the gel increased due to absorbtion in glycerol. In order to develop more suitable gels with methanoic acid for the control of varroa in bees, i.e. physical stability and the appropriate methanoic acid evaporation, more research will be needed.
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