Treatment of Honey Bees for Acarine Mite (Tracheal Mite) Infestation

Various Treatments that are (or have been) recommended for treating the Acarine or tracheal mite that infests honey bees, are listed on this page and the links that lead from it.

Folbex VA

Folbex VA used to be the preferred treatment for Acarine in UK, but has not been available for many years as it would be too costly to obtain a veterinary licence. However there is a linked page on Folbex VA which gives the details of how it was used when it was available.

Oil of Wintergreen

Also known as Methyl Salicylate, formula... C₈H₈O₃ It is distilled from various species of plants that stay green in winter, hence the name. It should be noted that there are different species used in UK to those in many US texts.

Somewhere between 1920 and 1925, Dr. J. Rennie, recommended wintergreen in preference to the original Frow treatment for treatment of Isle of Wight Disease (whatever it really was).

Between 1920s and 1940s it was common in UK for a wicked bottle of wintergreen oil to be kept in the bottom of the hives as a matter of routine, This was purported to control Acarine infestations, but I have seen no specific trial results on the effectiveness.

Manley used a small bottle (about 25 ml) of Oil of Wintergreen with a wick, or a small flat shoe polish tin with the lid perforated with holes of 6 mm to 9 mm. The tins were filled with cotton wool, with a disc of felt as the top surface, the cotton wool being completely saturated with the wintergreen. He kept such evaporators in all hives and mating nucs all year round.

The wick used has been reported differently in different texts, but such a wick is only a means to provide a large surface for evaporation and should not be critical. Three forms are mentioned... The first being cotton pyjama cord, the second being lamp wick (used in the flat tins by some), but the third requires a little explanation... It uses a soft cotton 'string' that was sold for knitting into dishcloths, six strands of this were laid parallel and loosely knotted close to one end, the long strands were fed into the small bottle and knot rested in or on the mouth and the short strands were fanned out to do the majority of the evaporating.

Menthol

In the United States Acarine is a big problem, they refer to the Acarine mite by the term 'tracheal mite', which of course, reflects it's method of infestation.

Bee treatment in the US requires approval by their food and drug administration department. Menthol crystals are the only US approved chemical treatment for Acarine or tracheal mites.

Menthol is a crystalline alcohol, formula... C₁₀H₂₀O It is obtained from oil of peppermint and is used in medicines, cooling salves and smoking materials.

Menthol crystals are used as a fumigant, the crystals sublime into the gaseous state as well as going through a liquid phase, but the process is very temperature sensitive. Vapour is released above 21°C and as the gas is heavier than air the crystals should be above the brood nest, however above a temperature of 27°C the vapour release rate becomes so high that the fumes may drive out the bees from the hive and so above this temperature the crystals should be placed on the hive floor (bottom board). If an Open Mesh Floor or screened bottom board is used the varroa monitoring board should be in position to close off the bottom of the hive even if no monitoring is actually taking place at the time (there may be some varroa mite lethality involved with menthol, but we are discussing tracheal mites here).

The evaporation rate of menthol not only depends on temperature, but on the physical size of the crystals and the method of containment, the dosage recommended by the Connecticut Agricultural Experiment Station is 50 gm made up into a flat 180 mm square packet formed from a plastic mesh of such screen size as to stop any crystals from falling out of the packet.

Duration of treatment should be between fifteen and twenty five days with outdoor temperatures around 20°C.

The timing of Treatment will depend on weather and nectar flows in your area, you should not use menthol when the colony has supers on. Generally an autumn treatment is most effective although you must have adequate temperatures.

Various formulations that mix the menthol with grease or vegetable oils in an attempt to obtain a continuous release of the gas into the hive have been tried, but the one mentioned below that uses paper towels has been given much promotion on the internet.

Shop towel method

The developer of this method, Allen Dick, has detailed the blue shop towel method on his diary pages.

Frow treatment

This method is no longer practiced, owing to the dangerous constituents and risk of cancer and so it's mention here is purely for historical interest.

The ingredients varied over time and with availability of components... Nitro benzene being involved in all formulations and generally the major constituent. Safrol, Ligrion, Petrol (gasoline) and Methyl Salicylate were all used as ingredients in different ratios and at different times.

Frow treatment was usually administered by giving small doses of about one millilitre on to a felt pad, daily or on alternate days, for a period six to ten days, then removing the pad after a further week to ten days.

Use of Sulphur

Flowers of sulphur (powdered Sulfur) has been recommended in some books and can be both sprinkled on bees or the bees may be fumigated by a smoker that has been lit and is going well having a teaspoonful of flowers of sulphur added to it. The bees are fumigated, late in the evening after flying has finished, in a closed hive that has its entrance blocked for about twenty minutes.

Part of the action of such fumigation will be due to sulphur dioxide but there is likely to be some Sublimation of Sulphur that occurs in the hot, oxygen starved, atmosphere that exists inside the smoker. The fine particles of sulphur that result will have a good chance of physical contact with an Acarine mite within the trachea of an infested bee.

Grease patties

The vegetable greases and oils used with menthol to produce a finely divided homogeneous mixture have been found to have a direct effect on the tracheal mite themselves. The vegetable shortening or oil interferes with ability of tracheal mites to transfer from one bee to another.

The recipe being one part by weight of vegetable lard (shortening) to two parts of sugar (finely granulated). Or if vegetable oil is used, then the ratio is one part by weight of vegetable oil to three parts of sugar (in this case 'icing' or powdered sugar may make the finished patties hold together better).

For delivery of this mixture into the hives, form the patty similar to a hamburger about 100 mm in diameter by about 9 mm thick and sandwich it between wax paper discs. To use, place the patty centrally on top bars of the frames within the brood box and peel off the upper wax paper disc.

Grease patties can be used in early spring and/or the autumn. As there is no 'active chemical ingredient' there are many claims that the grease or oil will not contaminate honey supplies, but I am not sure that this is totally true, nor am I convinced that there will not be contamination of the beeswax in the combs.