Can the honeybee survive?

Bee mortality

Over the past year, various media outlets have reported on massive mortality among honeybees in North America. Parts of the Netherlands have also experienced increasing bee mortality. How much truth is there to these reports, and is the bee mortality in the United States connected to that in the Netherlands? Should we look for causes in climate change, the varroa mite, the use of pesticides, or perhaps radiation from mobile phones? An article from December 2008 from the Dutch professional journal for enforcement officers in animal and environmental affairs (Dier en Milieu). Author: Henk Top.

A Dutch beekeeper speaks

Jan Piet Frens is one of the 7,000 beekeepers in the Netherlands. Jan Piet was a biology teacher and retired during the summer holidays. He has been a passionate beekeeper for 28 years. He lives on the Beusichemsedijk just outside Culemborg, where the river Lek flows in front of his house and the Betuwe region stretches out behind it with its orchards. Behind his shed, he currently keeps 17 bee colonies in hives. In spring, he places his bee colonies in the well-known cherry and apple orchards. In summer, he moves his bees to an area with many linden trees, and in autumn they go to the Veluwezoom, where heather blooms profusely during that season. On average, he maintains between 10 and 20 bee colonies, which varies per season.

Jan Piet explains that in the 1980s and 1990s, it was typical for about 10% of bees not to survive the winter. In recent years, he has observed a clear increase. In 2003 and 2004, he even lost 75% of his bees. He attributes the mortality largely to the varroa mite. The media sometimes suggests that this is a new disease, but beekeepers have been aware of this phenomenon for much longer. Jan Piet suspects that there may be multiple causes for the increasing mortality, which also depends on the region and the method of beekeeping. The impoverishment of species diversity in the field also plays a role when bees search for food. Furthermore, he is one of the bee health coordinators working closely with Wageningen University, where he closely follows the results of various scientific studies.

The Varroa Mite

Researchers such as Tjeerd Blacquière from Wageningen University are studying bee mortality. In recent years, he and his colleagues have conducted considerable research. He believes that the varroa mite is an important cause of the sometimes massive mortality among bee colonies. The varroa mite is a parasite originating from the Asian honeybee, Apis cerana. The Asian honeybee is reasonably resistant to this parasite, but the European honeybee is not. When this mite appeared in Europe around 1970 and in the Netherlands in the mid-1980s, it caused enormous damage. All bee colonies are now infested with it.

Additionally, the varroa mite is a host for various viruses. Jan Piet explains that the varroa mite lives in the beehive, feeding on the honeybee larvae. The bees build cells where the queen bee lays her eggs. A fertilized egg becomes a worker bee; an unfertilized egg becomes a male bee, a so-called drone. But first, a larva emerges from the egg. This larva is sealed in a cell by the bees so it can pupate undisturbed into a worker bee or a drone. The varroa mite crawls into the cell just as it is being sealed. It feeds on the pupating larva and reproduces within the cell. Between 2 and 5 mites emerge from a cell and crawl onto the bee to find other cells. The bee itself emerges deformed and weakened, for example with crumpled wings.

Jan Piet begins treating for the varroa mite in the hive early in the spring, using thymol and oxalic acid as advised by experts from Wageningen University. These substances can be dissolved in sugar water or introduced through misting or evaporation. He has the impression that this has resulted in decreased mortality among his bees in recent years. However, he immediately adds that a very experienced beekeeper in his area, despite conscientiously treating for the varroa mite, lost 80% of his colonies last winter. Clearly, there are multiple causes of bee mortality.

Massive bee mortality in the United States

Tjeerd Blacquière, bee expert at Wageningen University, states in an interview with Marcel Hulspas that the media gives the impression that the varroa mite is a new American phenomenon, but 4 to 5 years ago, massive bee mortality occurred in Europe, often in specific regions such as Northern Italy and Bavaria. The following year, the situation had returned to normal. In the United States, the massive mortality appears to spread over much larger areas. According to Blacquière, this is also related to how beekeepers work there. In the Netherlands, beekeepers work locally. They have a small number of hives that remain within a certain area. In the United States, beekeepers have thousands of hives. They transport them on trucks throughout the entire country, from Florida to California, wherever farmers or growers need bees. In this way, an infestation can spread rapidly across the entire country. Blacquière is very pragmatic about various speculations regarding causes of bee mortality, such as the greenhouse effect, the use of new pesticides by farmers, or radiation from mobile phones that could be lethal to bees.

Monitoring the health of Dutch bees

Blacquière attributes the main cause of bee mortality to the varroa mite in combination with various types of viruses. This is also evident from the bee health monitoring conducted by him and his colleagues at Wageningen University, together with 35 bee health coordinators, involving 150 Dutch beekeepers. On October 18, the first results were announced during the Bee Health Day in Wageningen. This monitoring provides information about potential disease-causing organisms in bee colonies, but not whether certain diseases play an active role.

The monitoring identifies the varroa mite as the most important disease-causing organism. The samples taken were also tested for viruses. This part of the research was outsourced by Wageningen University to the Central Science Laboratory in York, England. Three viruses often associated with massive mortality, including in the United States, were not found. However, three viruses were found that, according to the literature, are associated with the varroa mite. Infection with Deformed Wing Virus was lower than the researchers had expected, and together with Sac Brood Virus, its symptoms include crumpled wings, which are familiar to beekeepers. According to the researchers, it was striking that the causative agent of European foulbrood was found so frequently (in 36% of the samples). Not long ago, this disease was considered absent in the Netherlands. Clinically sick colonies are also being reported more frequently by beekeepers. The analysis of this monitoring still needs further development. The researchers now want to discover what can be learned about the spread of pathogens in the Netherlands, whether there is a connection with beekeeping methods, varroa control, and bee breed. But equally important for the researchers is to find out whether there is a connection between the various pathogens and whether some pathogens are always linked together.

Nosema ceranae

The monitoring also reveals that traces of nosema ceranae were found in 87 of the bee samples. This is an intestinal parasite, but the researchers at Wageningen University do not consider this alarming because, in their opinion, beekeepers can do much to prevent this disease by focusing on maintaining good bee condition. Romee van der Zee from the Dutch Centre for Bee Research, however, holds a completely different opinion. In 2006, she concluded that varroa mite control did not provide sufficient explanation for the high mortality (26%) occurring in the winter of 2005/2006 and that the real cause still needed to be found. In the October 2008 issue of the magazine Bijenhouden (Beekeeping), she writes that the existence of the parasite Nosema ceranae in honeybees was not yet known in 2006, and she concludes that based on research conducted by her center in 2007 and 2008 among 409 beekeepers, no reason was found to attribute great significance to the varroa mite as a cause of bee mortality in the winter of 2007/2008. She states that this confirms the observations of researchers who published earlier in the journal Science. In the September issue of Bijenhouden, Van der Zee points to the relationship between Nosema ceranae and massive bee mortality. She concludes that this parasite could well be an important candidate as a pathogen.

Her research also reveals large regional differences. In the provinces of Gelderland and Overijssel, the average mortality in the winter of 2007/2008 was 19.9%, while in the Hollands Midden area, mortality was as high as 51.4%.

Pesticides

Sjef van der Steen reports in an article on a symposium held in Bucharest in early October about the possible effects of pesticides on bees. Insufficient is known about the indirect or long-term effects of pesticides, or crop protection products as they are now called, on bees. During that symposium, extensive discussions were therefore held about guidelines for test programs that newly developed pesticides must undergo to be approved.

Another possible problem is seed coating. Various seeds from plants that bees visit, such as oilseed rape, and indirectly corn and sugar beets, are nowadays coated with a layer of pesticide. Such a pesticide is absorbed into the plant during growth and thus protects the plant against feeding insects. The pesticide Clothianidin, which is very toxic to bees, is used for this purpose among others. In the spring of 2008, mortality occurred in Southern Germany, France, and Italy because part of the coating landed on flowering plants during sowing. This application is also permitted in the Netherlands because normally bees and other pollinating insects do not come into contact with Clothianidin in this way. No problems have been reported here. Negative effects on bees from other types of pesticides are also known. Under laboratory conditions, it has been observed that some substances have a negative effect on bee respiration, while other substances disrupt orientation or temporarily affect motor function. Experts therefore consider it quite possible that pesticides contribute to the increased mortality among honeybee colonies. A monitoring program has been running in Germany since 2005 to gain more insight into this influence.

Conclusion

At this time of year, beekeepers such as Jan Piet Frens speak of winter bees, and if all goes well, the 17 colonies in the yellow-painted hives behind his house have been provided with a substantial supply of sugar to get through the winter. This year, on the advice of experts from Wageningen University, he has undertaken varroa mite control at the right time and in the right way using the most effective methods. He hopes that mortality among his bees will remain low during the coming winter and that spring will not come too early, because that would mean there are still too few plants in bloom and therefore too little pollen, which in turn has consequences for the development of his colonies, as the bee larvae would receive insufficient food. Such weakening can result in greater mortality because the bees would not have built up sufficient resistance to various parasites and viruses. So is there a connection with climate change after all?

It is clear that much research still needs to be conducted to properly understand and prevent the causes of massive bee mortality. The bee is an indispensable link in the ecological system and for the cultivation of various crops. Through the many interventions we as humans make in nature and the environment, we sometimes make it very difficult for these hard workers to properly carry out their important task.

Literature consulted

Blacquière, Tj. 2008, The health of Dutch bees; first results of monitoring
Blacquière, Tj. 2008 American foulbrood discovered through monitoring
Van der Zee R, 2008, Bee mortality monitor part 1. Bijenhouden, September 2008
Van der Zee R, 2008, Bee mortality monitor part 2. Bijenhouden, October 2008
Van der Steen S, 2008, Bees, bumblebees and pesticides
Cornelissen B. 2008, Bijen@wur expects winter mortality as a result of varroa
Hulspas M, 2007, An old enemy follows the bee, interview with Tjeerd Blacquière about bee mortality

Thus far the article by Henk Top.

Radiation from mobile phones

It was Albert Einstein, who researched nuclear explosions and radiation, who pointed out that if bees become extinct, humanity would suffer the same fate within 4 years.

The Swiss farmer Hans Sturzenegger in Reutlingen fought for many years against a transmitter mast forced upon him as a leaseholder by the telephone company Orange. The antenna was placed on the roof of a cow shed. Within three years, 31 calves went blind there. Sturzenegger and Orange finally agreed that the antenna would be rendered inactive for a period to see whether the cataracts in the eyes of calves born to mothers exposed to radiation were actually caused by emissions from the mast. Following the period of inactivity of the mast, the Bundesamt für Lebensmittelsicherheit und Veterinärwesen confirmed the farmer's suspicions, and the antenna was subsequently removed by Orange.