Wolfgang Ritter, President of the Apimondia Standing Commission for Bee Health.
International (OIE) and German National Reference Laboratory for Bee Diseases, CVUA, Germany
Many people are concerned about the future of the honey bee because of the great number of bee colony losses, particularly in the USA, as recently highlighted throughout the media. It is of such importance that the US House of Representatives held a special hearing to deal with the matter, and even the New York Times and the Journal Science published major features. As often happens, this creates media exaggeration ranging from ‘Bee AIDS’ to the extinction of mankind as a consequence of the loss of honey bees. To address the problem correctly, all the facts are needed.
How did it start?
During October-December 2006 beekeepers throughout the USA announced a dramatic spate of sudden bee colony losses. Many beekeepers observed for the first time that no dead bees remained either in front of, or inside the hives. They found empty hives and combs with brood of all ages and plenty of food and in certain cases, the queen along with some young bees, was still strolling over the combs. The Ministry of Agriculture immediately established a working group within the Agricultural Research Service (ARS) to examine initial test results and defined their observations as ‘Colony Collapse Disorder’ (CCD).
Initial surveys indicated losses in some apiaries of 30-90% but, as with all cases of this kind, it was difficult at first to get reliable data on the total losses. However, the extent of the problem became clearly visible when facts revealed that up to 700,000 colonies had died.
Is the problem new?
Similar symptoms with colony losses have already occurred in the USA: in Alabama and Minnesota in 2002 and 2004, as well as in California in 2005. But losses were also recorded outside the USA: for example in Australia and Mexico in 1975 and in those cases, this phenomenon was called ‘disappearing syndrome’.
In Europe, too, there have always been losses of bee colonies from time to time, showing the same symptoms. Extremely high losses were recorded during the winter of 2002-2003, estimated at 20% in France and up to 38% in Sweden. In Germany, an average of 32% of the one million bee colonies died and many beekeepers lost everything. The symptoms were more or less identical with those recently observed in the USA. In Germany this phenomenon is called Kahlfliegen. It first occurred in France about 15 years ago and can still be observed today: most of the colonies collapsing in harvest. Across the rest of Europe symptoms were numerous and varied, and ranged from brood of all stages left in the hive, few bees left in the hive until food stocks ran out, or cleared by robbing bees from stronger colonies.
How do bees avert diseases?
At first glance it seems strange that bees depart from their colony, leaving brood and food behind. To understand this you have to study the bee colony’s procedures for averting diseases. All actions of the single bee concentrate on one single aim: to guarantee survival and multiplication of the colony. The loss of one single bee does not matter. The colony’s health is above its own, even if this means the single bee’s death. The colony’s defence strategy against diseases therefore gives more priority to social behaviour than to the single bee’s own immune system. Recognising and removing ill brood is part of the defence mechanism of a honey bee’s make-up, and the removal of ill or infested bees is also important. This is achieved by preventing ill or otherwise ‘strange’ bees from entering the hive, or they do not return from foraging. Foraging and not returning to the colony, especially of old bees, is therefore part of the natural hygienic behaviour of the bees. It happens a hundred or a thousand times each day. A dramatic situation occurs only if the colony is not able to regenerate sufficiently, or if all of the bees depart within a few days. If a colony of African bees is severely infested by the Small hive beetle Aethina tumida, the process of departure happens in a co-ordinated way with all the bees leaving as if in a swarm. However, a colony of European Apis mellifera bees, for example with a serious Varroa destructor infestation, may react in a more disorganised way. In a Varroa-infested colony, infested bees leave the hive and invade other colonies in the nearby environment. This leads to an explosively increasing number of mites, and rapid colony destruction: this is immediately observed by a vigilant beekeeper. Collapsing colonies distribute thousands of mites to neighbouring colonies. You sometimes find within one week over 2,000 new mites in already treated colonies. They must have arrived via robbing bees or not returning bees.
What is the reason?
Empty hives, without reason, can complicate the issue as to why the bees left. Only if some bees or brood remain can one try to discover why. In spring, if you have heavy colony losses, in most cases Nosema spores can be found. For several years our examinations have shown that Nosema ceranae, which might have migrated from Asia, has been found. However, it also appears in surviving colonies, and very frequently, remaining bees are infected by the viruses transmitted by Varroa mites. The brood can also show additional infections with fungi and bacteria. It is still to be answered if the diseases diagnosed are the result of the reduced bee population and increasing stress in the remaining colony, or if they are actually responsible for the colony loss. Even if Varroa mites cannot be found in all brood cells, it has been assumed in Europe that this parasite is the cause. It weakens colonies to the extent that they become increasingly susceptible to other diseases and unfavourable living conditions. The latter is difficult to investigate and to quantify. This leaves room for all kinds of speculation. They range from the utilisation of specific pesticides, to genetically modified plants (GMOs), to radiation from mobile telephone masts. This list may be extended as long as you like.
Similar discussions are now underway in the USA. American colleagues point out that the symptoms appear in regions without any access to mobile telephone networks, and where no GMO crops have been cultivated. In the USA, until now, Deformed Wing Virus could nearly always be found in the remaining bees examined. This corresponds to our examinations in more than 300 apiaries in Austria, Germany and Switzerland in winter losses 2002-2003, when we nearly always found this virus. Recent examinations in co-operation with other European colleagues show that this virus, contrary to other bee viruses, only rarely shows genetic variations all over the world, and is therefore closely connected with the spread of the Varroa mite. For this reason it can be assumed that the Varroa mite represents one of the main reasons for the bee losses, and this includes the USA.
Certainly, the reasons are multi-factorial and regionally different. Of course, the human factor should not be neglected, influencing bee colonies not only by the way of colony management and disease control, but also by environmental conditions.
What is the difference between beekeeping in the USA and in Europe?
In the USA (and contrary to Europe), nearly all kinds of pathogenic agents play a role in bee health and can be found in many colonies. The managed application of medicines enables beekeepers to obtain good honey harvests. However, even the slightest interference overturns this system. This became obvious when, in the 1980s, the tracheal mite Acarapis woodi and later the Varroa mite Varroa destructor, and in this century the Small hive beetle Aethina tumida, were introduced.
As a rule, beekeeping in the USA is focussed upon a maximum honey yield or pollination capacity. This means that in extreme cases, according to the principle of ‘hire and fire’, bees are kept only for a short time under maximum exploitation, to be disposed of afterwards for financial reasons. Bee colonies that are kept throughout the year are also exposed to enormous stress because of extremely long migrations, artificial provision with cheap food, and colony management following strict time frames. Moreover, the bees are living in agricultural monocultures that greatly reduce the natural diversity of the bees’ diet. We know that pollen provides honey bee colonies with natural antagonists of bacteria, fungi or with antibiotic substances. But not every kind of pollen is equally suitable. If there is a lack of diversity, defence facilities decrease and the colonies become more susceptible to diseases.
In industrial agriculture we use industrial beekeeping. Pollination is an especially clear example. The agricultural monocultures require intense application of pesticides. As a consequence the pieces of cropped land reaching to the horizon are often deprived of natural pollinators such as flies and beetles. And this in a continent not formerly populated by pollinating honey bees: it was the settlers from Europe who introduced the Apis mellifera honey bee to the USA.
This requires the pollination capacities of bee colonies to be directed by humans according to strict time frames. The beekeeper profits from the financial value of this service: typically US$125 (€90) and more are paid per colony. So a beekeeper who is being paid for pollination services, can afford the disadvantage that the honey gathered, often polluted by pesticides, cannot be used as a food item. If the unique pollinator is lacking, then agricultural output will suffer, and the total damage may be huge. In the USA, the losses due to the reduced harvest of almonds and fruits are estimated at several millions of US dollars. That is why the outcry about losses comes not only from beekeepers, but even more from fruit-growing farmers.
What is being done?
The search for answers to this problem started years ago but up to now no satisfactory results have been achieved. It is of major importance that colony examinations are made before CCD sets in. Only when it is known how the development, the progress of diseases, and the environment of a collapsing bee colony differ from a healthy one, is there is a chance to understand the reasons.
Three years ago in Germany, the Federal Ministry of Agriculture and Consumer Protection initiated a monitoring project throughout the year in which bee institutes screened a total of 7,000 colonies belonging to 123 beekeepers from all over the country, by taking samples and carrying out regular examinations. Similar actions are planned in other European countries. To co-ordinate the approach and to exchange the results as rapidly as possible a European working group was formed. This network is now enlarged to other countries including the USA. By means of this co-operative effort it should be possible to solve this worldwide problem for honey bees and beekeepers.
First published in Bees for Development Journal #84