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translated from the original German by
Dr. Erich Kristen
Toledo, Ohio
United States of America


It will be exactly ten years in 1995 since I discovered the first Varroa mites in my bee colonies. I experienced a cold shower when I realized that this dangerous parasite had finally arrived. From this moment on many things had to be changed and adapted to this new situation. Beekeeping, as it used to be, was no longer possible. I can't forget how helpless my colonies were. I reported this in my first brochure in 1988. In 1990 I gave an account of my beekeeping during the year in my book, Imkern Heute, and also began to describe the first attempts of selection of bees, less assailable by the Varroa mite. Even though I treated my bee colonies only with formic acid, I began searching in 1989 for possibilities to develop a Varroa resistant bee. In this book I outline my operation over the past six years; that is from the beginning of my first tries of selection in 1989 until 1994. This is mainly observation of many bee colonies and development of a method that makes it possibleto recognize and measure the property of resistance against the Varroa mite.

Randegg in October 1994


It is extremely difficult to have a wish, not knowing whether it can be fulfilled, and if it can be fulfilled, how to go about it. This is exactly as it is in the search for Varroa resistant bee colonies. Every creature experiences pain and so does the bee that is attacked by the mite. The bee twitches shortly at the first contact with the mite. But this is mostly all that can be seen in the average bee. They are "dumb" and not smart enough to ward off these little parasites. It is quite different with the Asiatic bee. She has defense mechanisms that make it possible to keep the parasites in reasonable and tolerable limits. The Asiatic and the European bees are able to mate, but have no descendants. They are considered different species.

However, according to Prof. Dr. Friedrich Ruttner, the Cerana bee is a distant cousin of the Carnica bee and they have many similarities. But where and how should one search; and all this in addition to the heavy work during the bee season. Questions and questions and no answer. At least, that was the way I saw it in 1989. I asked myself what would happen to my 700 bee colonies - infested by the Varroa mite for years - if everything would be left to nature's law. Before the complete destruction of all bee colonies, there will surely be a few colonies that will live longer than the rest, whatever the cause may be. These colonies had to be found. Since I used only formic acid for treatment, there was no danger from side effects due to chemicals. Residues of chemicals in beeswax could possibly give a different picture of the amount of contamination. Hope and error would be in close proximity.

I was encouraged to the search by many colonies and the above mentioned conditions. I also realized the risk of losing many colonies and finding none or only very few clues for Varroa resistance.








The appearance of the Varroa mite in our bee colonies has changed beekeeping dramatically. In order to deal with it, one has to become familiar with the biology and biography of this parasite.

The parasite Varroa jacobsoni was named after the German researcher Jacobson. He found this mite for the first time in 1904 in the bee Apis cerana on the island of Java. Over thousands of years this bee race developed a symbiosis of bee - parasite. Probably beginning in Afghanistan, where Apis cerana is also at home, the mite was transmitted to our Apis mellifera and through China and Russia this dangerous parasite came finally to Europe. Shipments of queens hastened the distribution.

The female mite, the real vermin, is about 1.5 mm in size. The body of the mite is protected by an armor of chitin, colored light brown to black. The female mite has four pairs of legs; the first two in front are used as feeler. If one turns the mite on its back, one can sometimes observe, that the three posterior leg pairs move evenly while the front legs remain quite still or move in a different way. The sting and suction organ is between the front legs. With its help the female mite is able to pierce the armor of the bee and to suck out the hemolymph, the so called "beeblood".

The female mite enters the broodnest before the brood of the workers and the drones has been sealed. It moves to the floor of the cell into the remaining brood food. And there they remain without movement as if they were dead. After a few days the female starts laying her eggs. They develop into young mites - males and females. The fertilization of the young females ensues right there in the brood cell. These descendants exit the cell with the young bees and drones. The mites infest the bees, sucking fresh blood, and return later back into the broodnest for further propagation. This is a general outline of the breeding of these parasites. If there is no broodrearing by the bees, there is also no propagation of the mites, but the mites are able to survive these brood pauses. The damage starts in the brood of the bees and may result in the death of the brood or in the development of crippled bees, both workers and drones. Some may have no wings. Further damage continues with thefull grown bee. The mite enters between the abdominal scales of the bee. There she is well protected and undisturbed, sucking the blood of the bee. The next damage to the bee can result by infestation of the bite wound with different pathogens. Every single mite in a bee colony causes harm. A fast growing population of bees will be able to survive minor damage by the mites. But if the mites are able to propagate en masse, then the bee colonies will destroyed within a few weeks.
Illustr. p.9: The abdomen of a Varroa mite. Left and right of the body the four legs. The two front legs - erected - developed as feeler. Between these the sucking and stinging organ.
Illstr. p.10 top: One Varroa mite under the electron microscope: legs, front legs and the stinging organ are clearly visible.
Illustr. p.10 bottom: Young bees damaged by the Varroa mite. Some exit the brood cell without wings. A terrible sight.
Illustr. p.11 top: The internal part of the mite is visible after the back armor has been removed. The strong muscular system is visible.
Illustr. p.11 bottom: A close-up of the same picture. Marked and strong bundles of muscles in the front part of the mite. This explains why it is so easy for the mite to jump from the comb on to the bees.
Illustr. p.12 top: One bee colony killed by Varoatose (death by the Varroa mite). Afterwards it was burglarized (robbed out). Die Wachsmotte (wax moth) has started to destroy the combs.
Illustr. p.12 bottom: Another colony killed by Varroatose before any treatment against the mites. The wide belt of pollen in the bottom hive body indicates that this has been strong colony. The last brood was forsaken by the bees.


In my beekeeping, I use only formic acid to get rid of the Varroa mite. The Pharma Industry offers frequently new drugs against the mite, but not once did I use these offers. Whenever they come out with a new remedy, they assure us that it is the best and, if used as directed, no remaining residues are to be expected. After years and usually when a new drug is released, one finds out about the disadvantages and dangers the old one produced. If there are residues of these drugs in the bee wax, they are well preserved between the skin of the nymphs in the cells of the combs.
After the melting of wax of the old combs, there is the possibility, that some residues are concentrated in the middle walls. For this reason, I think formic acid is less dangerous. The problem, of course, is how I can use it best against the mite without causing any danger for the bees. But in the five years I have used this method, I learned enough by experience that I employ formic acid only. With this statement I don't want to imply, that this treatment is the only one for every beekeeper. But my treatment is a very effective alternative to different procedures.
Illustr. p.14: Acute state of Varroa invasion. At the start of the treatment with formic acid, the bees were already damaged. Sudden disappearance of the summer bees. The second hive body is empty.


Advantages: Formic acid is in very small concentration an ingredient of nectar and honey dew.
The vapors of the acid kill the mites. With this treatment there is also a certain disinfecting of combs and brood.
The acid vapors in high concentration penetrate the cover of the cells and kill the Varroa mites.
Formic acid is harmless to the environment and is quickly neutralized with water.
Disadvantages: The acid evaporates according to temperature.
Iron begins to rust faster and earlier by contact with the acid.
Open honey will take up the vapors of the acid. Therefore it can be used only outside the honeyflow time.
Loss of a queen (or lots of queens) can never be completely excluded by the use of acid. Open brood will be corroded with strong concentrations and will be removed by the bees.

My experience with formic acid.
In my brochure "Varroatose wirklich kein Problem mehr" in 1988 I related my experience with the treatment of the mites with formic acid. Since then, nothing important has changed. I disliked the necessity of treatment within short periods of time. I was able to remove this problem to a large degree. This year I have not lost one single colony due to Varroatose. The reason for this is due to the kind of operation that makes a quick recognition of a susceptible colony possible. Those I treated before any other colony. But also the changed preparation of the formic acid boards are advantageous.


Chemical formula: HCOOH. Its name derives from the forest ant Formica Rufa. The acid was discovered in 1670 and recovered by distillation. Her chemical properties were first ascertained by J. Liebig.
Properties: Formic acid is a watery clear, very acid liquid with obnoxious fumes. It can be mixed with water, ether and alcohol in all proportions. The vapors are flammable and burn with a blue flame.
Occurrence in nature: Formic acid can be found in small amounts in the animal kingdom, and then mostly in insects. But it is contained in many plants, partly as free acid, partly as ester. For example in the needles of firs, stinging nettles and in many fruits. And as a salt in human urine. It can even be found in inorganic nature, as in some mineral waters and during fermentation by yeast and bacteria. By mixing oxalic acid with glycerin, formic acid was so produced in 1855.
Illustr. p.16: Formic acid (85%) in a large container with distribution cock. In small amounts formic acid is a natural ingredient of honey. Used in the right dose it is disinfecting and kills mites in the bee colonies.
The use of formic acid (p.17)
There are numerous possibilities for the use of formic acid. It is used in the production of hard rubber, in the textile industry, for producing synthetic material and in the leather industry for the disinfecting of hides. In special solutions formic acid is used in medicine for some rheumatic diseases of the joints and in homeopathic dilution for gout.
Because of its antiseptic properties, formic acid is used for conservation of fruits and fruit juices. This is legal with the addition of 0.25% formic acid. (Ed. note - remember he is referring to what is legal in Austria not in the USA - consult local law.) Barrels are also disinfected with the acid. It is also used in agriculture and in the production of dyes and pharmaceutics. And for the past ten years to combat the Varroa mite.
Toxicology: Breathing in the fumes of formic acid may be harmful. Touching it leads to skin burns. The skin should be washed off immediately. Small drops on the skin may be diluted by saliva. The work place should be well ventilated.
Free formic acid can not last in the human body. It is converted to salt and dissolved by the body fluids. 1 g formic acid per kilogram of an animal body is deadly. A daily intake of 0.07 g is supposed to be harmless for the human body.
This short extract of the literature (Chemielexikon and Ullmanns Enzyklopädie) shows the wide use of formic acid and emphasizes caution handling this acid.
Illustr. p.18: Filling the container with formic acid. The container has two openings. In one opening a pump (measures exact amounts) is screwed in, the other opening for filling in the acid.


There is the dispensary which can measure up to 50 milliliters. The container, made of acid resistant synthetic material and the necessary hoses. The exact dosage measuring device and the closed system make an accident unlikely.


Commercially there are several Weichfaserdämmplatten (material as in peg boards ?) available with different abilities to soak up liquids. Boards that soak up the acid very slowly are not well suited.
Preparation for the take up of the acid by the board: Each board is placed in a small Nylon sack, 25 x 40 centimeter. Through the opening of the sack I instill the desired amount of acid onto the board. After the board has been soaked with the acid, I close the sack and leave the acid to soak in for a few days.
Illustr. p.19: The size of my board for the treatment is 20 x 13 cm and 15 mm thick. On the longer sides I have cut out a portion with a circular saw. In this way the thickness in the middle is reduced to 1 cm. On the shorter sides, I leave an edge of 2 cm for gripping the board when soaked with acid.
Within several days, the formic acid is evenly distributed and the board enlarges like a sponge. If one board, treated in this way, is placed in a colony with a temperature behind the plastic sheet of about 25 degrees Celsius, then the evaporated formic acid is reduced by 1/3 in the first 5 hours in comparison to a board placed into the colony right away after soaking with the same amount of acid. For this reason was I able to use a higher dose with prolonged effect. I leave the boards soaking with 70 milliliters for at least three days, if the temperature is below 20 degrees Celsius. 60 milliliters for one day, if the temperature is 25 degrees Celsius. 50 milliliters for several hours, if the temperature is 30 degrees. For an extreme invasion with mites in some colonies, I keep several boards with 100 milliliters at hand. These should be soaked for 3-5 days. I use these boards in colonies with a sudden invasion with mites of the brood of the workers of over 50% in July. With thismethod, I achieve the complete destruction of all mites.
A good time for the installment of the boards is the early forenoon. The temperature at this time behind the sheet is about 15 - 20 degrees Celsius.
Illustr. p.20: The desired amount of acid is instilled into the Nylon sacks. I close the sacks by twisting the opening and keep them in well sealed cans.
With increasing temperature, evaporation increases. The temperatures at noon and early evening in the shade and in the colonies behind the sheet, where the board has been installed, are about the same. If a board is installed with a temperature of 30 degrees, one can count on a sudden and strong evaporation. The coolness in the evening and at night gets only slowly into the colony. In such case I treat with 50 milliliters. The vapors infiltrate first the upper hive body and penetrate the brood nest from below and from the sides. The effect in both hive bodies is about the same, regulated by the boards in the hive bodies. Only in the combs up front is there a diminished effect. The danger of a sudden extension of the vapors is reduced by placing the board behind the plastic sheet. The vapors extend first into the free room behind the sheet and invade the breeding nest evenly from below and the sides. The bees and the queen are not surprised too suddenly by the vapors. (Ed. note - theframes in Alois Wallner's colonies are parallel with the entrance - those in the USA are perpendicular. Mr. Wallner uses a plastic sheet to restrict the space available to the bees - removing frames not in use if needed or desired. He places his formic acid boards in the empty space behind this sheet - this is explained more fully in Imkern heute. Thus the plastic sheet is a barrier that slows the formic acid fumes penetration into the brood nest - he obviously believes this is helpful in minimizing the harm to queen and colony)
Illustr. p.21: The board of the last treatment is removed and a new soaked board installed. The board does not have to be touched directly, because the sack is used for protection.
In the past few years we had extreme high temperatures in August. That made the treatment with formic acid more difficult. These high temperatures cause a more rapid evaporation of formic acid and may cause a greater loss of queens.
After many experiments I found it advantageous to expose only about half of the board. I pull out half of the board from the sack and place the board with the opening on top behind the sheet. Formic acid will be brought from below by capillary power and evaporated from the upper part of the board. I increased the dosage from 70 to 80 milliliters.
I never expose more then half of the board if the day temperature is 30 degrees Celsius and more. Even after days is there a good evaporation of acid.
The only disadvantage: The sacks are sometimes gnawed at by the bees and have to be replaced with the next filling.
Duration of treatment (p.22): This depends on the amount of infestation, but also on the time of the first treatment. As a rule I treat two times or maximally three times. The first treatment with the second feeding and the second one with the last feeding at the end of August. If I still recognize a strong infestation, then I will install another board - in the above described way - with warm weather in September. The selected colonies and the breeder colonies on their resistance stand and their selection stand will not be treated. They will be treated only if there is too much infestation of the brood. These colonies will then be removed from further selection and breeding and placed on the outer stands (yards).
Monitoring Varroa infestation: I open the newly sealed cell with a pointed forceps and look for infestation in the cell and on the Streckmade (propupa).
Formic acid kills Varroa mites in the brood.
If there is satisfactory concentration of formic acid then it penetrates the seal of the cell and kills the mites in the brood.
Illustr. p.22: Control of the success with formic acid treatment. Dead Varroa mites on the Steckmade (propupa) exhibit the effectiveness of the formic acid in the brood.
Illustr. p.23 top: The board leans against the sheet. Only half of it is out of the sack. This prevents a too rapid evaporation.
Illustr. p.23 bottom: View from above into the hive body. The acid board sits on the frame of the lower hive body.












In the first week of May 1989 I made a very interesting observation while working with my colonies. On controlling (inspecting) one colony I had removed the honey super and put aside. Between the two frames I found some drone brood comb. This is not unusual. By moving the frames this construction became torn and several pupae of drones were exposed. There was one Varroa mite on one pupa. The mite moved forth and back on the pupa. While I observed this mite, something special happened. I almost could not believe what I saw. There was a bee a few centimeters away from the pupa. Suddenly this bee ran wildly toward the pupa. I thought that the bee wanted to remove the uncovered pupa, but the bee grasped the mite with her mouth organ. I noticed that the bee caught the mite with her mandible in a horizontal way from the front. One third of the hind part of the mite was still visible in front of the mandible. Then, with the mite in her mouth, the bee took off. This was an unique observationthat I have not made again.

Illustr. p.26: Varroa mite with bitten off legs.


The brood of drones and the Varroa mite.

Infestation of the drone brood is 5-10 times more frequent than that of the worker brood if the mite has this choice. This seemed to me a first clue for selection. But how? Since I had installed a drone half frame in each colony to lure in mites, no more work had been necessary. In 1989 I had the opinion that, for selection purpose, I should not cut out the drone brood comb. Until the beginning of July I left the comb for the propagation of drones. Unfortunately, this also led to an increase in the Varroa population. In the beginning of July I started to cut out the brood of drones and estimated the amount of infestation. I found in most colonies a marked infestation level, many times up to 100%. Sometimes I monitored hundreds of colonies without finding a significant lesser infestation level. This discouraged me greatly and sometimes I thought my efforts a waste of time. In many colonies some weakness was recognizable and treatment against the mite was many times too late. Andstill I found on about 5% of my colonies a infestation level of 20 to 30% in the begin of July until the middle of this month. The price to pay for the selection of these 30 colonies had been high.

15 of those 30 colonies I took home, the rest I left on their individual stands. All 30 colonies I treated with formic acid, as I did with all other colonies. I had selected a few colonies with apparently lower susceptibility for infestation . Because of the great loss I could not continue to use this method in 1990 and had to find a better procedure.

I had no answer to the question why there was lesser infestation in those colonies. Winter came and I had more time to think everything over and I remembered the experience from last summer when a bee caught a mite. If this had not been a single event, then I should be able to find injured mites on the floorboard, since the bees would not be able to remove dead mites during winter. I put a good size piece of white construction paper into several colonies who showed a lower susceptibility for infestation. Anyhow, I was curious how much normal mite fall would be. I took a magnifying glass with 20 x enlargement several days later and saw that some mites showed leg injuries. I did not know how significant that might be. I took about 10 of those injured mites to have them photographed. At this time I had no idea that one would need a electron microscope to do the job. But this I found out and I also found Prof. Dr. Ferdinand Rusicka of the University of Vienna who took the picture withhis electron microscope. And when I saw the pictures, I had no doubt, that the injuries were caused by the bees. I found only months later how important this discovery was.
Illustr. p.28 top: Varroa mite with severe injuries on her legs caused by the bees.
Illustr. p.28 bottom: Varroa mite with severed legs. After injuries like these, the mite will die within minutes.
SUMMARY OF 1989 (p.29)

In this year I looked for less susceptible colonies for the first time. In May I observed a bee that caught a Varroa mite with her mandibles.