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In the past year various reports have been published on massive fatality among honeybees in North America. In parts of The Netherlands, an increase in bee fatality has also been noticed. How much of these reports is true and is the bee fatality in the United States connected with that in The Netherlands? Perhaps we should we look for causes in climate changes, use of pesticides or even radiation from mobile phones?

Jan Piet Frens, a recently retired biology teacher, is one of the 7000 beekeepers in The Netherlands. He has been a passionate beekeeper for 28 years. He lives just outside Culemborg, The Netherlands, where the river Lek flows in front of his house and at the back the area known as the “Betuwe” stretches out with all her orchards. He currently keeps 17 bee colonies in hives behind his garden shed. In Spring he sets the bee colonies free in the neighbouring, well known cherry and apple orchards. In the Summer he moves his bees to an area where there are many lime trees and in the Autumn they are brought to the Veluwezoom , an area where heather blooms profusely in that season. He keeps an average of between 10 and 20 bee colonies. This varies per season. Jan Piet explains that in the Eighties, it was quite commonplace for about 10% of bees not to survive the Winter. He has noticed a definite increase in fatality during recent years; in 2003 and 2004 he even lost 75% of his bees. He blames the parasite the varroa destructor to a large extent for these fatalities. The media often raises the suggestion that there is a new disease among bees, but beekeepers have been aware of this phenomenon for quite some time. Jan Piet suspects that are more causes for the increase in fatality, but they will more than likely be connected with the region and the manner of beekeeping. Degeneration of the natural species diversity also plays a role when the bee is searching for food. Furthermore, he is one of the bee health-coordinators working closely with the Dutch University of Wageningen and he meticulously follows the results of all sorts of scientific studies there.

The Varroa Destructor
Researchers such as Tjeerd Blacquière from the University of Wageningen are concerned with fatality among bees. In recent years, he and his colleagues have conducted extensive research. He considers the Varrao Destructor to be an important cause of the often massive fatalities among bee colonies. The Varrao Destructor is a parasite which comes from the Indian honeybee, Apis cerana. The Indian honeybee is reasonably immune to this parasite, but the European honeybee is not. When the parasite appeared in Europe around 1970 and in the mid-Eighties also in The Netherlands, it caused immense damage. All bee colonies are now contaminated by it. Added to this, the Varrao Destructor carries various viruses.
Jan Piet explains that the Varroa Destructor lives in the beehive, from the honeybee larva. The bees build cells, where the queen bee lays her eggs. A fertilised egg becomes a normal bee, an unfertilized egg becomes a “worker” or a drone. Firstly, a larva comes out of the egg. This larva is closed off in a cell by the bees, so that it has the chance to develop into a drone. The Varroa Destructor crawls into the cell at the moment the cell is closed off. It lives from the developing larva and reproduces in the cell. Some 2 to 5 parasites emerge from a cell and they crawl onto the bee in order to find other cells. The bee itself comes into the world deformed and weakened, with wrinkled wings, for example.
In the early Spring, Jan Piet starts fighting the Varroa Destructor in the hive. As advised by the University of Wageningen, he uses oxalic acid and thymol . These substances can be dissolved in sugared water or can be introduced into the hive by means of evaporation or nebulising. He has the impression that these methods have resulted in a decrease in fatality among his bees in recent years. However, he hastens to add that a very experienced beekeeper in his neighbourhood lost 80% of his bees last Winter, despite his conscientious attacks on the Varroa Destructor. There are obviously more causes of bee fatality.

Massive fatalities in the United States
Tjeerd Blacquière, bee expert at the University of Wageningen says, in an interview with the Dutch Scientific journalist Marcel Hulspas, that the Press gives the impression that the Varroa Destructor is a new American phenomenon. However, 4 or 5 years ago there were massive bee fatalities in Europe, often in particular areas, such as Northern Italy and Bavaria. The following year the situation had recovered. In the United States it looks as if massive fatalities are spread out over much wider areas. According to Blacquière this also had to do with the way beekeepers worked there. Beekeepers work locally in The Netherlands, they have a small number of hives and they remain within a certain area. In the United States beekeepers have thousands of hives. They transport them in trailer trucks throughout the entire country from Florida to California, to all places where farmers or breeders need bees. In this way, contamination can spread rapidly throughout the country. Blacquière is very down to earth about speculations as to the cause of bee fatality, such as the greenhouse effect, or use of new pesticides by farmers or radiation from mobile phones.

Monitoring the health of the Dutch bee
In Blacquière’s opinion, the most important cause of bee fatality is a combination of the Varroa Destructor and various types of viruses. This is also evident from bee health monitoring at 150 Dutch beekeepers, done by himself and his colleagues at the University of Wageningen in collaboration with 35 bee health-coordinators. On 18 October last, the first results were announced during the bee health- day in Wageningen. This monitoring yielded information about potential pathogenic organisms in bee colonies, and not whether certain diseases played an active role.
The monitoring shows the Varroa Destructor to be the greatest pathogenic organism. The specimens taken were also tested for viruses and this part of the research was sent out to the Central Science Laboratory in York, England. Three viruses often linked to massive fatality, in the United States, amongst others, were not found. But three viruses were found which, according to documentation are connected with the Varroa Destructor. Infection by the Deformed Wing Virus was lower than the researchers had expected, the symptoms of which are wrinkled wings and these are familiar to beekeepers. The researchers were surprised that the origin of European foul brood was so often found (in 36% of the specimens). Not so long ago, this disease was considered not to be present in The Netherlands. There are also more and more reports of clinically sick colonies from beekeepers. Further analysis of the monitoring needs to be done. The researchers now want to look into what can be discovered about the spread of pathogens in The Netherlands. Is there a connection between the method of beekeeping, combating the Varroa Destructor and the type of bee?. But just as important for researchers is to see if there is a connection between the various pathogens and whether some pathogens are permanently linked.

Nosema ceranae
Monitoring also shows that in 87 of the bee specimens traces of nosema ceranae were found. This is an intestinal parasite, but the researchers at the University of Wageningen do not consider this to be cause for alarm, because in their opinion the beekeepers can do a lot to prevent this disease by concentrating on keeping the bees in good condition. Romee van der Zee from the Dutch Centre for Bee research has, however, another opinion. In 2006 she came to the conclusion that combating the Varroa Destructor did not provide sufficient explanation for the huge fatality (26%) in the Winter of 2005/2006 and that the real cause still had to be found. In the October edition (2008) of the magazine Beekeeping (Bijenhouden) she writes that the presence of the Nosema ceranae in honeybees was not known in 2006 and she comes to the conclusion that on the basis of the research that was conducted by her Centre in 2007 and 2008 among 409 beekeepers, no reason was found to appoint the Varroa Destructor the main cause of bee fatality in the Winter of 2007/2008. She says that this confirms the observations of the researchers who had published earlier in the journal “Science”. In the September issue of Beekeeping, Van der Zee points to the relationship between Nosema ceranae and massive bee fatality. She comes to the conclusion that this parasite could very well be an important candidate for the pathogen. Her research also shows large regional variances. In the provinces Gelderland and Overijssel, the average fatality in the Winter 2007/2008 was 19.9%, whilst in the are Hollands Midden fatality was as high as 51.4%.

Sjef van der Steen reports in an article on a symposium that was held in Bucharest at the beginning of October on the possible effects of pesticides on bees. There is not enough known about the indirect or long term effects of pesticides or of plant protectors (as these are called nowadays), on bees. During that symposium extensive discussions were held about guidelines for test programmes which newly developed pesticides needed to undergo in order to be approved.
Another possible problem is coating seeds. These seeds from plants visited by bees, such as coleseed and more indirectly, corn and sugar beet are coated nowadays with a layer of pesticide. This sort of pesticide is absorbed in the plant during growth and in this way protects the plant against gluttonous insects. The pesticide Clothianidin, extremely toxic to bees, is used for this purpose. In the Spring of 2008 fatalities occurred in Southern Germany, France and Italy because part of the coating landed on flowering plants when being sown. This practice is also allowed in The Netherlands, because in the normal way, bees and other pollinating insects do not come into contact with Clothianidin. There have been no problems reported here. Other negative effects for bees caused by pesticides are also known. In laboratory conditions it has been observed that some pesticides have a negative effect on bees’ respiratory system, whilst others disturb orientation or cause temporary problems in the central nervous system.
Experts deem it quite possible that pesticides contribute to the increased fatality among honeybee colonies. In Germany a monitoring programme has been under way since 2005 to gain more insight into this influence.

At this time of year beekeepers, such as Jan Piet Frens speak of Winter bees and if all is well, the 17 colonies in the yellow painted hives behind his house have been given a large amount of sugar to come through the Winter. On the advice of the experts from the University of Wageningen, he has started combating the Varroa Destructor at the right moment and in the right way, using the most effective remedies. He hopes that fatality among his bees will remain low during the coming Winter and that Spring will not come too early, because that would mean that there are too few flowering plants and too little pollen, which in turn would have consequences for his bees, because the bee larva would have insufficient food. Such weakening could lead to greater fatality, because the bee would have built up insufficient resistance to all sorts of parasites and viruses. Has it to do then with climate change?
It is clear that much research needs to be done into the causes of massive bee fatalities and into a solution. The bee is an essential link in the ecological system and for growth of a number of plants. The many invasions we as humans make into nature and the environment make it extremely difficult for these hard workers to carry out their most important task.

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