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Fighting Varroa
Without challenges life would be quite boring. But the Varroa mite is more than a challenge. It's a threat.

The problem number one in beekeeping is the Varroa mite. Problem number two is the Varroa mite and problem number three the Varroa mite. That's how Dr. Peter Rosenkrantz opened a lecture in Sweden some years ago.

Without Varroa beekeeping would be much easier, almost as in the old days. Not that there were no big die offs back then. It was. But not in such a continuous way as is often the case today.
Without Varroa there would have been no CCD (Colony Collapse Disorder). But CCD is much more than Varroa. And there are die offs due to Varroa we don't call CCD. CCD and Varroa die offs are caused of cocktails of pathogens and poisons.

But a good summary of what CCD is, is how Chris Baldwin in South Dakota, a treatment free migratory beekeeper with 1500 colonies put it:

Poisoning of the earth.
Origin of Varroa
The original host of the Varroa mite is the Asian cousin of our bee, Apis cerana. Cerana and Mellifera are so closely related that they even mate sometimes, but the offspring eggs only develop very little before they die. It is discussed which variety is the more original than the other, cerana or mellifera.

In the 19th century our western honeybee, Mellifera, was taken to different places in Asia where the eastern honeybee, Cerana, lived, Japan, Primorski, India, etc. Transports continued. More bees were brought to Primorski area and bees were brought back closer to Europe from there. Cerana was brought to western countries for research.

In the middle of the 20th century, about 100 year after the initial transportation of Mellifera bees to Asia, these bees began to develop big problems from the mites, in Asia, and in Europe. 1968 a Cerana colony was brought to Germany by a scientist and in 1973 the first colonies died there because of varroa. But the mites were close by in the Balkan countries anyway, Primorski types of mites. And soon they had reached Finland too.

Why did it take almost 100 years to create real problems in our type of bees? Whatever reason, it was probably more than one, as is often the case. Of course mites were transferred to Mellifera right away when they met Cerana. Of course mellifera bees sometimes robbed cerana colonies and vice versa.
The chemical mistake
The Europeans did a big mistake back then in the 70:s. They only focused on chemicals to fight the mite. We aquiered some good knowledge quite soon about how Cerana fight it. Bees can fight it. They are not like sheep trying to fight wolves. They can be good fighters. Already early on it was clear cleaning out of invaded brood cells is a key trait. One variety of this is today called VSH (Varroa Sensitive Hygien). But chemicals were in the front. The South Americans in Brazil were the first to show us a non-chemical solution for the bees.
To Sweden
Of course Sweden would not be left out of the fellowship of Varroa fighters. In 1987 the mite reached the port of eastern Gotland, the island in the Baltic. 1991 it reached the port of Malmö, on the mainland of southern Sweden. 2007 it was seen in my apiaries.

We had about 150 000 bee colonies and maybe 14 000 beekeepers in the 80:s. Today we are fighting to be above 100 000 colonies and 11000 beekeepers. Many beekeepers have too often severe winter survival problems connected with the presence of Varroa. Not only Varroa though is responsible for die offs.

Chemicals in Sweden
We have two approved so called veterinary medicins to fight the mite, Apigurd, which is an organic treatment based on thymol, and Apistan, with the active ingredient tau-fluvalinate. Today Varroa mites are showing resistance to Apistan at several places in Sweden.
Acid resistant gloves are needed when handling Apistan and organic acids like Oxalic and Formic acid. Protective mask with an appropriate breathing filter is needed when working with Oxalic and Formic acid. When working with Apiguard and Thymol just ordinary gloves is a good choice.
Besides approved drugs, we can use what we call ”not forbidden” chemicals, organic types, supposed low poisonous chemicals. But how low poisonous they are could be discussed. In this group we find organic acids and essential oils.
After a few years of treating against Varroa in southern Sweden, an extreme example was a colony with some 500 mites that produced almost only crippled winged bees, due to DWV, deformed wing virus (Kjell-Erik Ohlsson). Organic acids were used. Where Apistan has been used this has not occured in such a dramatic way. The most virus susceptible bees of course die. The survivors will create a stronger stock.
Treatment strategies
For many years mostly two types of strategies against the Varroa have been used in Sweden.

– Drone brood cutting and organic acids is a strategy called organic.
– The other is the use of Apistan.

In the beginning formic acid was the most used organic acid. Today many have shifted to oxalic acid. What is called organic treatment is supported by the association. The use of acids is shown to be well possible to give good results. But in practise it is not so easy to achieve consistent low winterlosses.

Investigations have shown that official winterlosses may in average reach around 30% some years in some areas. For the whole of Sweden this type of official statistics mostly show 15-20% winterlosses. For different beekeepers winterlosses have differed between 15-90%. Some have managed to never reached these figures, but have kept figures of 5-10% winterlosses. They have shifted treatment methods every year, often in a three year cycle.
The weakness with this official statistics is that that it’s built upon voluntary reports each year. The percentage of the beekeepers that contribute with figures are mostly below 50%.

With Apistan averages has often been around 10%, before mites started to become resistant to this treatment. Apistan and synthetical miticides have negative effects in that they are giving residue problems with the wax. Either the original poision or secondary degradation products.

Thymol, like in the approved veterinary medicine Apiguard, was not talked about much or used much at first. It isl considered an organic treatment. The use of thymol is increasing rapidly as a reaction to difficulties using organic acids properly and because it’s so easy and cheap to make your own thymol pads.
Thyme contains a lot of thymol naturally, as much as it gives a clear taste. Lime as well. You find thymol in spice and toothpaste.
The active substances used in Apilife Var is only slightly soluble in Water, but are fat-soluble. Due to their high volatility, Thymol residues in wax decrease quickly. Accumulation of the product is unlikely even with prolonged use. Though small amounts can always be present. During the process of recycling the wax the concentration of thymol is not reduced. If combs are ventilated, the concentration of thymol decreases quickly. No tendency for increase of residues from one year to the other was observed. In 1993 in Hohenheim 0.2 mg thymol per kg of honey was detected in average of more than 100 samples of spring honey. According to WHO, a residue of thymol in food are safe for the consumer, as long as it doesn’t exceed 50 mg/kg. In a test of Federal Dairy Research Institute with more than 500 consumers, honey containing thymol was tested. Only residues more than 1.1 mg/kg of rape and acacia honey could be detected. If the product is properly used and temperatures are optimal, the expected efficiency is higher than 95%.
After Imdorf A. Bogdanov S .; Kilchenmann V., Maquelin C. (1995)
A new varroacide with thymol as the main ingredient. Bee World 76 (2) 77-83.


A similar paper with some additional interesting information:

One of several texts showing the value of Thymol as a food preserver and showing medical properties:
This graph is showing the difference between the results of the figures for winterlosses concerning the same winter from the voluntary reports and from figures gathered from telephone interviews with the aim to reach all beekeepers in this district. The conclusion is that beekeepers that have lost a lot of bee colonies are more hesitant to voluntary give figures about their winter losses.
Higher winterlosses
With the spread of Varroa and use of chemicals against it we have seen increased virus problems, which probably is due to a lowered immune system with the bees caused by among other things miticide chemicals. The use of plant protection chemicals and mites becoming resistant to miticide chemicals have increased the losses of bees. This is probably because of synergetic effects between the pathogen nosema, chemicals and viruses.

The plant protection drugs called neonicotinoids have been used quite a lot in Sweden like in other countries. Some are forbidden now. No poison is beneficial for bees, but it's difficult to know for sure how much neonics contribute to the die offs. Probably the many types of other kinds of bees, in first place solitary bees, are more in danger from this type of drugs. A synergetic effect with nosema and viruses is shown in studies made, so it's no surprise if problems are showing up where neonics are used a lot.

Many stress factors
Honeybees are faced with many more stress factors nowadays than in older days. Every stress factor that can be eliminated is invaluable. Evidently they are too many today. One stress factor the beekeeper can do something about more easily than others is what they themselves put into the hive.

Longterm solution
A longterm sustainable solution to the Varroa problem is breeding resistant bees. John Kefuss in southern France has done that. He hasn't been using any treatment in his original stock for more than 15 years. His winterlosses are normal. Several beekeepers have now been treatment free in USA for more than 10 years, for example Kirk Webster and Richard Reid. Often there are feral bees in the neighborhood and often those beekeepers have at least 3 km to other beekeepers’ bees. In Norway there is a couple of beekeepers, Hans-Otto Johnsen and Terje Reinertsen, with several hundreds of hives that havn’t treated against varroa for more than 10 years. And the mite populations in their hives are naturally very low. Institutions and beekeepers are working on this path now more and more, in Europe and in America.
A photo from a lecture by Dr Peter Rosenkrantz kaveing a lecture in Sweden some years ago. He talked about a test in Germany. The donor colony was probably robber by bees from the other colonies and shared thus a lot of mites with other colonies, here up to 1.5 km away (1 mile). Probably even a colony 2 km away would have picked up some mites. A heavily infested colony doesn't have much of a defense system left.
The ISHS study shows how much bees sometimes can drift, here when moved for pollination purposes.
The JAR study show how both drifting and robbing can be invilved in evening out mite populations among colonies in apiaries.
The super super organism
To work with Varroa resistant bees you have to be aware of some things. Bees do not stay in their own hive. Many end up living in another hive than the one in which they were born. And bees visit each other for different reasons, for example to steal food. During these processes they spread parasites and pathogens. So if a colony is a super organism, an entire apiary is maybe a super super organism. Even bees within some distance can influence each other. Is the limit distance maybe 3 km?

Start breeding
So if you start working with resistant stock don't expect all your colonies to be resistant, or even the ones in which you introduced your new queens, after buying just a few queens. The strategy has to be applied on a broader scale. But it can be a start. Start with one apiary with only as good resistant queens as possible and as isolated as possible. Then increase the area with more apiaries. Read more about this in the next article
“Breeding resistance”.