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EXPERIENCE WITH THE USE OF LACTIC ACID AGAINST VARROASIS

by Kaplan Bernhard Euteneuer

Markt 13 D.5483 Ahtweiler

From “Bienenwelt” Dec.1989 pp 259-260

Translated from the original German by A.E. McArthur M.I.L.

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Since 1985, when I discovered Varroasis after a diagnostic treatment in my apiaries I have taken note - as I am sure have many of my beekeeping colleagues - of the leading discussions about the right medication which least affects bees and honey in the fight against Varroasis. Many beekeepers publicise the fact that they only use the medication allowable under the law at any time. In the discussions about systemic or contact pesticide treatments I have deep reservations, even when during the treatments only the smallest amount of the active ingredient finds its way into the honey. By virtue of working with bees there is always the urge to try new ideas on the bees and to experiment. This makes beekeeping for many of us the more interesting. Variations are made with the authorised anti-Varroa medication such as Perizin, Folbex VA (neu) and Formic acid. I heard recently from a beekeeper who, in order to limit the progressive contamination of his honey comb, dispensed Perizin (or whichever active substance ) in a shallow dish on top of the frames, dissolved in sugar syrup, from which the bees could take up the medication.

I myself prefer a winter treatment of my colonies using pure lactic acid (C3H6O3).

Why lactic acid?

1. Lactic acid is an absolutely “natural” treatment. It exists in small amounts naturally in honey, even we humans are aware of its effect, when after strenuous exercise we later experience stiffness in our muscles.

2. Lactic acid is an effective anti-Varroa treatment. This has been clearly stated in a variety of reports and has also Been published in the specialist literature. In contrast with formic acid, which due to the fanning ability of the bees, has an effectiveness of from 0% to over 90%, lactic acid is sprayed directly onto the bees, where it is most effective. This procedure limits, especially in winter, the amount of lactic acid which can be applied.

3. Dilute lactic acid is virtually harmless. The beekeeper does not require to wear protective goggles when applying lactic acid and in my opinion the vapour produced is harmless ( in contrast with the likewise naturally occurring formic acid anti-Varroa treatment.

An argument against lactic acid is that it does not vaporise readily. In my experience this not the case, since the lactic acid (diluted to 18%) by virtue of the evaporating acid in the colony is immediately effective. The evaporation of the lactic acid even results in a residue of glass like platelets being formed which the bees remove and let fall to the floor board. Further to this I have even observed bees imbibing the lactic acid. The application of lactic acid is admittedly more time consuming than with other treatments. The winter treatment however results in the treatment being done at a time of minimal labour input in the beekeeping calendar.

I use 90% lactic acid from E. Merck (Darmstadt) product number 366, for the treatment of my bees. In contrast to the cheaper 60% lactic acid procurable at the chemist, which has a yellowish colour, the lactic acid which I used is water clear.

Winter Treatment of Bee Colonies using Lactic Acid.

Even if beekeepers of the old school raise their eyebrows: In order to have the colonies free of brood during treatment, it occurred to me to treat the colonies during the dormant winter period. Our bees in winter - at least when the disturbance is short duration - are not so vulnerable as was thought in earlier times. The first commandment for the beekeeper was - in winter - hands off the colonies.

In my opinion an ambient temperature of 3 -4 °C using an 18% lactic acid solution treatment is ideal. I apply the treatment (approx 12 ml per comb side) in the late afternoon at the beginning of December. To this end I remove all the occupied frames from my rear-management hives and free standing hives and placed them on a frame stand. I then take each frame in turn and spray the clustering bees using a plastic spray bottle of the type which is freely available in any hardware shop, until the bees are wet. The amount of fluid to spray on each frame of bees is a matter of experience: not too much, not too little. By virtue of the relatively high temperature existing in the colony, relative to the ambient much of the lactic acid evaporates immediately, The treated combs are placed back into the hive immediately after being sprayed. The bees create a transient increased temperature in the cluster, causing the cluster to expand somewhat, in the course of the evening the cluster quickly settles down. The inserted floor inlay is withdrawn the following morning. Using this procedure I have killed around 3000 mites in one particular colony(!) with a single treatment. Using Perizin as a control treatment another nine mites were killed. In conclusion I would like to state that there are no adverse effects on the bees or the queen in the use of lactic acid. Queen loss due to the treatment is negligible, even if the queen is also sprayed directly. It is recommended in my view that a second lactic acid treatment as described should be applied in early spring - directly after the first cleansing flight. This causes the residual mites which have aged during the winter to fall to the floor board insert.

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