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.

The Varroa mite is not the only big threat, but with this mite viruses of different kinds easier can parasitize the bees. It is these viruses that kill bee colonies. Without the mites, honey bees would not be exposed to many chemicals which are used to kill mites. These chemicals have a bad effect on the bees' immune and defense systems. There are also many other chemicals today which the bees get in contact with, plant protection chemicals in agriculture. But without the mite killing chemicals the bees would bee able to cope with the other chemicals and disease agents much better.

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 an often occurring way as is often the case nowadays.

CCD

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 embryos only develop very little before they die. It is discussed which honey bee 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 evident cleaning out of invaded brood cells is one 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 have maybe 120 000 colonies and 11000 beekeepers. Many beekeepers have had worse winter survival problems after the arrival of the Varroa mite. No surprise. Not only Varroa though is responsible for die offs. Maybe the high death rates have declined somewhat recently. Could that be due to that the standard cell size on wax foundation has become 5.1 mm instead of previously for many years 5.4?

Chemicals in Sweden

We have had 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.

Recently, three additional drugs have been approved for sale for use in hives. Apivar with the active chemical Amitraz. VarroMed - a solution with primarily oxalic acid, but also some formic and essential oils. VarroMed is intended for use in a similar way as an oxalic acid solution, ie dropped in comb gates with bees when there is no brood in the colony. Polymer with the active chemical flumethrin, a pyrethroid. Tau fluvalinate is also a pyrethroid, so Polyvar can not be used successfully in areas with Apistan-resistant mites.

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.

The beekeeper can prepare treatments with these substances for use in bee hives against varroa, but prepared mixtures and preparations with this purpose may not be sold. Just like the beekeeper can mix oxalic acid solutions, you can make dish cloth pads with thymol.

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.

After a few years of treating against Varroa in southern Sweden, an extreme effect 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 type of effect 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 was 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 Swedish Beekeeping 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 have reached in average 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 reache these high figures, but have kept figures of 5-10% winterlosses. Some of these 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 winter loss 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 in Sweden. It is 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.

Many have reprted good results using these home made thymol pads. An advantage with these is that you can use them also in spring without adverse effects on the bee colony.

The thyme contains a lot of thymol naturally, it gives a clear taste. Lime contains thymol as well. There are thymol in spices and toothpaste. Thymol is an antioxidant that is considered to have positive food preservant and medical effects.

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.

Neonicotinoids

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 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

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 involved 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 rob 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 about 2 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".