Abstract Since the middle of 2006, more and more beekeepers have been experiencing regular or repetitive losses from 50 to 90 percent of their hives. Although losing honeybee hives during winters is natural, the scope of such losses was more than expected. In this context, professionals and researchers in biology have come to recognize these losses under the name Colony Collapse Disorder (sometimes also called Fall Dwindle Disease). The causes of CCD remain unknown, and scientists are vainly trying to determine the ways in which honeybees could potentially respond to the emerging problem. In the current state of research, a detailed analysis of literature may shed the light on some out of many controversies associated with CCD. Colony Collapse Disorder Introduction Since the middle of 2006, more and more beekeepers have been experiencing regular or repetitive losses from 50 to 90 percent of their hives. Although losing honeybee hives during winters is natural, the scope of such losses was more than expected. In this context, professionals and researchers in biology have come to recognize these losses under the name Colony Collapse Disorder (sometimes also called Fall Dwindle Disease). The causes of CCD remain unknown, and scientists are vainly trying to determine the ways in which honeybees could potentially respond to the emerging problem. In the current state of research, a detailed analysis of literature may shed the light on some out of many controversies associated with CCD. Background CCD became one of the distinguishing features of honeybee loss since the middle of 2006: more and more beekeepers were complaining at losing large amounts of honeybee population without any visible reason. “In colony collapse disorder (CCD, honey bee colonies inexplicably lose their workers. CCD has resulted in a loss of 50 to 90% of colonies in beekeeping operations across the United States” (Cox-Foster et al, 2007). Sometimes, beekeepers lost 100% of their honeybees during one season. The growing interest toward CCD, however, is not in that it causes huge honeybee population losses, but in that these losses are not caused by any of the well-known honeybee diseases, including pesticide poisoning, the deadly larval disease, varroa mites, or starvation is also natural in winter.
The more scientists are trying to determine the only single cause of such colony losses, the more confused they become at the variety of possible reasons as well as their insignificance and irrelevance in terms of CCD. In this context, special attention has been paid to the role, which infections and microbes may play in the development of CCD and similar disorders in honeybees. Possible causes Case studies and professional researches list several potential causes of CCD, but none of the existing chemicals is solely responsible for CCD in honeybee populations. Researchers name viruses and immune disorders, pathogenic microbes and pesticides, but they cannot find a single agent or their combination that results in the development of CCD. Possible stresses that cause CCD include varroa mite parasites, poor nutrition, and pollination of plants with low nutritional value or nectar scarcity, as well as contaminated water supplies (James & Pitts-Singer, 2008). Literature review In her article, Watanabe (2008) provides an extensive review of the information that is currently available about CCD. Watanabe (2008) refers to David Hackenberg, an experienced beekeeper from California who was among the first to notice that some of his hives were empty. CCD damaged only adult population of bees, leaving healthy brood intact, and at the point of CCD development Hackenberg was confident that it was due to an environmental toxine and stressful apicultural practices that honeybees were dying in hundreds (Watanabe, 2008). Since that time, much about CCD has been learned, but for many professional and amateur beekeepers it is still a mystery; that is why Watanabe (2008) finds it appropriate to speak about parasites. Certainly, honeybees can be loaded with parasites; among those, varroa mites are fairly regarded as the biggest and the most dangerous types of parasites damaging bees. These feed on bee hemolymph and wreak havoc in bee hives (Watanabe, 2008). Another parasite usually called “tracheal mites” uses bees’ breathing apparatus and suck out their hemolymph.
Potentially, microsporidia may also be responsible for large honeybee colony collapses, but generally, honeybees are also vulnerable to a whole set of chemical insults, including in-hive insecticides, in-hive antibiotics, and environmental pesticides (Watanabe, 2008). Stress is sometimes included into the list of the major colony threats. None of these viruses and environmental threats seems to be directly responsible for what we currently know as CCD, but researchers are trying to prove that pesticides may be directly responsible for the loss of honeybee populations, because their metabolites are readily identified in pollen, wax, nectar, and bees themselves (Watanabe, 2008). Throughout the course of research, the list of possible pollutants has been limited to include only in-hive chemicals and agrochemicals, but the difficulty is in that physiology of bees in summer is much different from than in winter, and determining the environmental factors that are responsible for CCD is almost impossible. Some scientists suggest that CCD can be the result of the combined impact of stress and pesticides, because pesticides cannot be solely responsible for the development of CCD in hives. Moreover, it can also be a combination of pesticides, but the question is why these pesticides damage large bee populations, if bees have natural defense mechanisms. Moreover, the question is why bees lose these defense mechanisms and become vulnerable to external influences and forces. In this context, Cox-Foster et al (2007) pay special attention to microbes that can potentially contribute in Honey Bee Colony Collapse Disorder. In their article, Cox-Foster et al (2007) also mention that in case of CCD, “no dead adult bees are found inside or in close proximity to the colony. At the final stage of collapse, a queen is attended only by a few newly emerged adult bees. Collapsed colonies often have considerable capped brood and food reserves”. After reviewing the genome-sequence databases from several samples collected in Switzerland, Germany, and Africa, the researchers have mainly concentrated on Israeli acute paralysis virus – an unclassified virus that is often associated with CCD (Cox-Foster et al, 2007). IAPV was first described in 2004, when bees displayed the progressive signs of paralysis and were gradually dying outside their hives. When it came to CCD, bee colonies from Australia displayed similar symptoms, but pathogenicity of IAPV in different regions may also change or increase by other stressors like poor nutrition or pesticides. Again, Cox-Foster et al (2007) mention varroa mites as a possible cause of CCD, but both Watanabe (2007) and Cox-Foster et al (2007) have any compelling evidence to assert that it is due to varroa mites that honeybee colonies die in thousands. Discussion Does that mean that we will never be able to find the most relevant reason of CCD? Moreover, why is it that the public is so much concerned about the possible causes of CCD in honeybee populations? The truth is that honeybees are extremely important to the agricultural sector. “Bee pollination is responsible for $15 billion in added crop value, particularly for specialty crops such as almonds and other nuts, berries, fruits, and vegetables” (USDA, 2008). About one out of three products we eat daily benefits of honeybee pollination, making bees the integral components of successful food production. James and Pitts-Singer (2008) write that “there had been much-hyped press interest in reports (mis-reports as it turns out) of links between bee decline and mobile phone technology”. Whether under the impact of mobile or any other technology, it is obvious that the whole population of bees is gradually declining, and if in the middle of the 1940s the earth could boast having more than 5 million bees, honeybee population now has shrunk to no more than 2.5 million (USDA, 2008). Of course, with so few bees at hand, agricultural workers can hardly hope to gather good crops. Crops are deteriorating; so is honey bee colony health. There are still enough bees to supply all needed pollination, especially during spring and summer, but CCD leads to the growing price of honeybee hives. The growing price is caused by the growing demand for quality bee populations, which under the impact of CCD are harder and harder to achieve.
Scientific literature mentions several incidents of mass bee colony collapses at the end of the 19th century and at the beginning of the 20th (James & Pitts-Singer, 2008), but there is no compelling evidence to the fact, that CCD was the main reason of those collapses. What seems to be true is that none of the current researchers has been able to produce a theory that would at least be close to realistic. Pathogens, pesticides, microbes, and viruses – all these are given equal place among the probable causes of CCD, and while honeybee populations are gradually vanishing, beekeepers do not even suspect how they can prevent or at least minimize the risks of an unknown disease. On the one hand, CCD can be the result of the whole combination of factors, and may be due not to physiological but biological features (for example, peculiarities of honeybee organism functioning). On the other hand, CCD can remain a mystery, without any hope to resolve it. Simultaneously, it is more than important that researchers resolve the major CCD controversies in the nearest time, as far as the shrinking bee population is likely to produce negative impacts on the quality and quantity of accessible crops all over the world. Conclusion CCD remains the topic of the major biological concern. With the growing scope of the collapsing colonies, crops and agricultural businesses may carry significant economic losses. Unfortunately, the specific causes of CCD remain unknown. Among the most probable reasons of such collapses are microbes, environmental factors (pesticides), viruses, and other types of stresses. Being unable to determine a single and the most relevant cause of CCD, researchers suggest that a whole combination of factors can be responsible for the development of such disorders in honeybee populations. Honeybee populations continue to decrease, and the public should be particularly attentive to these types of honeybee losses, bearing in mind the role and importance, which bees have for nature and environment. Obviously, the scope of losses caused by CCD will only increase, and unless we are able to invest in various types of biological researches, we will hardly arrive to objective and reliable conclusions in the nearest future.