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
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 VARROA MITE (p.7)
TREATMENT WITH FORMIC ACID
THE DOSIMETER FOR FORMIC ACID
MY "DEMITING" DISH
THE VARROA MITE (p.8)
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
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.
THE TREATMENT WITH FORMIC ACID.
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
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 AND DISADVANTAGES OF THE TREATMENT WITH FORMIC ACID. p.15
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
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
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.
THE DOSAGE MEASURING DEVICE
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
MY BOARD FOR THE TREATMENT (p.18)
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
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
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
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
Monitoring Varroa infestation: I open the newly sealed cell with a
pointed forceps and look for infestation in the cell and on the
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.
AN IMPORTANT OBSERVATION
ALL BEGINNING IS DIFFICULT 1989
BEE YEAR 1990
CONTROL OF INFESTATION OF THE DRONES
DEVELOPMENT OF INFESTATION IN THE WORKER BROOD
CONCLUSION: YEAR OF THE BEES 1990
AN IMPORTANT OBSERVATION (p.26)
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.
ALL BEGINNING IS DIFFICULT
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.