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Posted 22 June 04

Silent spring in northern Europe?

Börje Svensson, Sala, Sweden

Reproduced with kind permission from
Bees for Development Journal 71 (June 2004)


Individual bees are very delicate organisms existing within the strong and resistant body of their colony, inside its carefully protected cavity. Honeybees have been surviving this way since long before man first stepped on earth (Free et al., 1982). An individual bee will freeze to death within minutes in the climate of Sweden where I have been keeping bees for 28 years. Colonies of bees have survived my mismanagement, infestation with wax moth, queenlessness, wet insulation, or even being tipped over during a cold winter storm. Some of my colonies always survived and managed to multiply when the spring sun shone and brought flowers and nutritious food back into the life cycle again. Winter losses never ever exceeded 15% - until last year.

Unwelcome experience

Winter 2002-2003 was a totally new experience for me and for thousands of my colleagues in countries like Austria, Belgium, Denmark, Finland and Germany. I lost 50 colonies out of 70! Only 20 survived. One neighbour lost 95 out of 120, someone else 24 of 25 and so on.

Some colonies died even in December. I found colonies that had just stopped living. They had given up life without any sign of struggle. They were dead without visible reason. They had plenty of good sugar feed. Pollen stores were available. The queen was sitting dead in the middle of the cluster. Other colonies tried to survive but gradually dwindled away with less and less bees and finally gave up before the warm weather could help them to recover.

I had a terrible job to clean up all the dirty comb and contaminated hives. The combs had to be brushed off before being melted in water so that the sugar remains could be separated from the pure wax. It is always a depressing job disposing of dead bees knowing their important task for maintaining good pollination in our neighbourhood.

Immediate survey

Our National Beekeepers’ Federation, SBR, reacted without delay and organised an instant survey within a random sample of 2,520 beekeepers (Kristiansen, 2003). From the 1,654 responses we can conclude that the colony losses in my county were about 36%. The national average was ‘only’ 20%.

A similar survey of 6,072 German beekeepers came up with an average of 29% winter losses during the same winter (Otten, 2003). The Swedish survey could not make any conclusions about any particular cause of the winter deaths but rather speculated that the event was a combination of unfavourable circumstances during the season 2002.

However there are several observations that can rule out some of the theories proposed:

1. Both experienced and less experienced beekeepers had problems.

2. The death toll was high also in areas where the Varroa parasite has not yet arrived.

3. The death toll was high also in areas where other diseases such as foulbrood, sacbrood, chalkbrood or nosema are rarely seen.

4. The death toll was high also for colonies in very well insulated hives.

5. The winter death was very low in the forest areas of northern Sweden but at the same time very high in the farmland area in northern Finland.

6. The death toll was high both in areas affected by the radioactive Cesium137 downfall from the Chernobyl accident as well as in non-affected areas.

More bad news

So we are many beekeepers who have hoped until now that the scientists are correct: that it was an extremely bad year of a kind that appears once in a while. But is it really like that? The sun is now warming up the hive bodies and the snow is rapidly melting away. The first Crocus flowers are beginning to provide pollen and Salix will soon follow. A first summary of my remaining colonies is again a catastrophe!!! Only 17 colonies surviving out of 30!!! And some of the survivors are very weak and may not make it another 2-3 weeks. My phone is ringing. Beekeeper friends are reporting: 7 of 8 dead, all but 2 dead, more than 50% dead and so on. It is too early to see if this is as serious a problem as last year, but this time I am not going to wait before raising my voice.

Possible explanations

We have to find resources and support to find out what is happening to our bee environment. What are the possible explanations? How can researchers join hands to determine how to overcome these problems? To start the discussion I would like to present a list of possible explanations that can be thinned out or extended with contributions by those who have a better view. Please join the debate with your own observations or theories.

1. The European Commission has decided to allow use of a number of doubtful pesticides. Some of these were banned in Sweden for many years such as Amitrole, 2,4-D, Linuron, Mecoprop, Paraquat, Propineb, Thiram and Bromoxynil. Many of these are extremely hazardous to humans but the objections from our government chemistry authority had no effect on the decision makers in Brussels. These pesticides are mainly herbicides and fungicides and most likely we will not find one of them that is used all over the affected region.

2. The European Commission has authorised a large number of new pesticides for an even larger number of different uses without adequate hazard testing. The new generation of pesticides can be generalised as: i) low dosage, ii) long persistence, iii) systemic action, iv) difficult to detect in laboratory tests. The Swedish government authority is also complaining in their annual report (KI, 2003) that it is difficult to keep track of the different pesticides due to many changes of ownership within the private sector.

3. The aphid pests (Megilethes.spp) on oil-seed rape have developed resistance to the most popular pyrethroid pesticides. Therefore the chemistry authority again approved use of the extremely bee poisonous insecticide Fenitrothion (Sumithion or Folithion) from year 2001. This pesticide was banned more than 20 years ago due to its enormous risks for bees, other insects and aquatic life.

4. The use of insecticides increased in Sweden 2001-2002 by 250%. A possible reason is that the warm summers (global warming?) caused heavy growth of aphid colonies in many grain crops.

5. A new range of pesticides has entered the market during the last five years. These are all based on the active ingredient Imidakloprid, a chemical that affects the digestive neurosystem of insects. Popularly we can say that insects that come into contact with these products lose their appetite and stop being harmful to crops. These insecticides have long persistence and a systemic effect. It is therefore possible that the harmful effect will occur over a long period and only gradually in a bee colony that is slowly during winter consuming its stored reserves of plant material. The treated seed will for instance germinate in August 2004, the plant will flower in June 2005 and bees will collect and store contaminated nectar and pollen that can cause indistinct symptoms during the winter 2006, one and a half years later!

Here is a list of Imidakloprid products being registered in Sweden:

-Chinook for seed dressing of oil-seed rape seed.

-Gaucho and Montur for seed dressing of sugar beet seed.

-Prestige for dressing of potatoes before planting.

-Confidor for treatment through irrigation water in green houses (ornamental plants, tomatoes, cucumber and sweet pepper).

-Merit Forest for treatment of forest plants against insect attacks.

-Some products are also registered for use in homes as dip sticks for indoor plants.

Commercial representatives also confirm that these products have been tried as seed dressing on wheat and oats. They are however not willing to disclose to what extent farmers are using seed treated with these chemicals. In France Imidakloprid pesticides have been banned for use on sunflower crops after heavy protests from beekeeper groups.

6. Pesticides in sugar cultivation or industrial manipulation of white sugar may be another problem for bee colonies. Use of the above mentioned systemic seed dressers on sugar beet seed (point 5) or insecticides on sugar cane fields can be a hidden problem. Also new techniques for extraction or bleaching of white sugar may cause a possible hazard to bees. An increasing trade with sugar products has also been noted

7. Extensive use of desiccants (Glyfosat, Rambo, Roundup) for total extermination of weeds instead of mechanical cultivation. The total usage of these herbicides has increased four years in a row. This is remarkable since the increase of Glyfosat products took place at the same time as the acreage of ecological farming also increased. This must imply that the intensity of Glyfosat usage has increased on the farmland that is still cultivated with chemicals. Several Glyfosat products are also registered for use by gardeners.

8. Increasing downfall from burning of household waste material as an energy resource. A new government fee on dumping of waste products has created an enormous interest for using household waste as an important energy resource. Large municipal heat and power plants have been converted from charcoal and crude oil to household waste and other biomass sources. The disadvantage with this quick change is that the cleaning techniques for many dangerous organic substances in the smoke are still rudimentary. In some cases we do not even know what to look for. The amounts of downfall may be very small but still extremely hazardous to human and other life from the very stable organic substances that come with the smoke from waste burning. Examples of such substances are PCB, Toxafen, Dioxin, halogenated flame retardants, nonylphenol, organic tin compounds, phthalates and secondary residues of all these products etc.

I do not claim that I have any proof for any of the above theories. What is of paramount importance is that we try to find out the cause for the winter deaths of honeybee colonies during the last two years. Will my bees survive another winter like this?

Or will we meet a silent spring next year?

If bees cannot survive can we?

Börje Svensson, Sala, Sweden (author)


Free, J.B. ed. (1982) Honeybee Biology, Central Association of Bee-keepers Publications, Ashford, UK.

Kemiinspektionen (2003) Sold quantities of pesticides 2002, KI, Stockholm, Sweden.

Kristiansen, P. (2003) Vinterförlusterna 2002/2003, Bitidningen (7-8), 13-14.

Otten, C. (2003) Daten und Fakten zu den Völkerförlusten, ADIZ 37 (8/2003), 6-8.


From the author – May 2004

We are beginning to see the full size of the problem now. In my county it seems like more than 50% of colonies died this winter.

The media is beginning to take notice now, but some of the news is old, as far back as 1999 from France!


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