What colony collapse disorder is really about

Size: px

Start display at page:

Download "What colony collapse disorder is really about"

Stanley Dennis Parker
6 years ago
Views:

1 What colony collapse disorder is really about Insect Behavior Skylar Biggs

2 Theories explaining CCD Colony collapse disorder (CCD) is characterized by the rapid loss of honeybees (Apis mellifera) within an affected colony, most commonly during the winter months. There is a minimum amount of individual worker bees that is required to ensure that the colony is at a functional capacity. When this minimum number of workers decreases the colony is unable to function and begins to collapse ultimately affect their ability to thermoregulate during the winter (Dainat et al, 2012). A general study was done by Vanengelsdorp et al (2009), they found that infected colonies had 3.5 times more death than in the control colony. The CCD colonies were weaker compared to the control colonies and colonies that were neighboring the CCD colonies became affected. This suggests that CCD may be contagious or there was a common risk factor that was present between both colonies. Betti, Lindi and Zamir (2014) took a different approach when it came to studying disease and its affects on the honeybee population; they decided to study the spread of disease and how it affects the underlying demographics within the colony. They focused on two factors that affect the survival or collapse of a colony; these two factors are rate of transmission and disease-induced death rate. They found that if the bees are infected at an early age or there is an increase in the transmission rate there are deleterious effects. The timing of infection also had an impact, if the infection occurred within 20 days to the beginning of winter the colony was at the most risk of infection. The most compelling results were that an infectious disease was more detrimental to the bee population than an environmental hazard, both of which having the same death rate. According to Smith,et al (2013), there has been a decline in colony numbers over a long period of time which has 2

3 had significant environmental impacts. It is thought that the cause of this long-term decline is due to many factors but the exact contributor is unknown. There are several factors that are thought to be contributing to CCD some of which are pathogens, insecticides, and parasites. There is a parasitic mite that was introduced to the honeybee population in the U.S. as well as Europe between 1970 and This parasitic mite is Varroa destructor and has been found to contribute to great losses of honeybees in Canada and a majority of Europe. Varroa destructor is detrimental to the health of the honeybee, this mite according to Boecking and Genersh (2008), injuries the honeybee by taking hemolymph which is essential for organ development. V. destructor prefer to invade the drone larva, after penetrating the royal jelly the mother mite lays her eggs. While the mite larva are going through the stages of development they feed on the hemolymph that is produced by the bee larva. If this mite does infect a colony and is left untreated it can lead to a collapse in the colony. Deformed wing virus (DWV) is among many viruses that affect the honeybee population; this virus is specifically associated with transmission from Verroa. destructor commonly referred to as varroa mites. It is characterized by pupal death and altered wing and body structures in adult worker bees. According to Ryabov et al (2014), there is a relationship between DWV and V. destructor in which DWV in the absence of V. destructor cause an asymptomatic infection. When V. destructor is present there are high levels of DWV, both of which contribute to altered adult development and ultimately increased mortality. Deformed wing virus has been found to affect the life span of worker bees in colonies that did not survive the winter. These colonies showed a high proportion of DWV infected bees during the winter when the colony died (Dainat et al, 3

4 2012). During the winter months the dead colonies had high levels of mite infestation, during these same months DWV was also found in high volumes among the dead colonies. Pesticides are thought to be one of the factors that lead to CCD, Chensheng et al (2014), explored the role of that neonicotinoid had on bee colonies. When neonicotinoid is used as a pesticide it is sprayed onto the plant where it is able to be absorbed into the soil. The roots from the plant begin to take up the pesticide through the soil; the chemicals then get transferred to the pollen and nectar. They found that both the control and the neonicotinoid colonies progressed virtually the same until the approach of winter. There was a decline in colony numbers both in the control and the neonicotinoid colonies when the temperature began to decrease. While the control colony was able to increase their colony numbers in the beginning of January the neonicotinoid colony was still declining in size. It was observed that in all of the neonicotinoid colonies all of the bees abandoned their hives during the winter months. Although there was a decrease in colony numbers in the control nests they were able to increase in size and re-populate by the end of winter. It appeared that in this experiment exposure to neonicotinoid only affected the bee population during winter and had no affect on population during summer and fall. The reason why neonicotinoid is damaging to a bee colony is because the chemicals present in this pesticide have damaging effects on bee development. Neonicotinoids in sub-lethal levels have been known to affect colony performance, more specifically in foraging and larval development. The chemicals in neonicotinoids have had negative effects on learning and memory while also affecting the central nervous system. When exposed to this pesticide it has been found that the bee colonies are more 4

5 susceptible to disease and affects hive hygiene (Sluijs et al, 2013). Pesticides such as neonicotinoids may not always be lethal to a bee colony, according to Sandrock et al (2014), sub-lethal neonicotinoid exposure did not increase colony losses during the winter months. Furthermore there were both short-term and long-term impacts not only on the colony but also the queen, suggesting that neonicotinoid does weaken bee colonies. While it is unknown if one or a combination of these causes are contributing to CCD the evidence is clear that the honeybee population is decreasing and colonies are being weakened. International vs. Domestic honeybee populations According to Dainat et al (2012), as of 2012 the United States was the only country that had documented cases of CCD. It was thought that CCD was not the only explanation for loss of bee colonies during the winter months however the other causes are unknown. Although CCD accounts for roughly 4% of colony loss it is still concerning because CCD is still such a mystery. As of 2013 the long-term decline in colony numbers seems to be more significant in the United States compared to Europe. When comparing the decrease in colonies the United States showed a 60% decline where as Europe only showed a 25% decline (Smith, et al 2013). Not only is the number of colonies decreasing but also there is an annual loss of colonies that is increasing. This loss of colonies in the U.S. and Europe is likely caused be a decrease in the beekeeper industry however more research needs to be done. It is still thought that this decline in colony numbers can be attributed at least in part to pathogens and pesticides. 5

6 There is a strain of bacteria that causes European and American foulbrood, which are both diseases that affect the honeybee populations. The European foulbrood affects the bee larva and is currently prevalent and increasing in the number of cases in the UK (Vanengelsdorp and Meixner, 2009). American foulbrood affects the bee brood and is highly contagious. American foulbrood is able to spread rapidly and easily, in order to prevent spreading this disease affected hives are burned and destroyed. Weather and Climate Honeybees are able to adapt to new climates and changes in weather forcing the bees to adapt to a new array of predators, pathogens and pests however a drastic change in either climate or weather may not have the same effects (Conte and Navajas 2008). This means CCD may not be the only contributing factor when it comes to the collapse of honeybee colonies. Weather and climate has been found to affect the welfare of bee colonies. According to Le Conte and Navajas (2008), climate change does have an impact on behavior and physiology. Climate change can affect the harvesting capacity of the colony based on the quality of the floral environment. If the temperature is too extreme such that if there is a lack of water from the flowers the bees will die. Climate change does not only affect the colony and bee population as a whole it can affect the development of bees as well. When the weather is cool the bees huddle into a ball and use stored honey as a source of energy to get through winter. If in the spring there are colder temperatures the bees are unable to go harvest, resulting in depleted honey storage. With this depletion of honey and not enough energy to harvest the bees starve to death. 6

7 The climate can affect flower development, which is directly correlated with bee populations and survival. If the weather and climate are both too dry the flower is unable to produce an adequate supply of nectar, without this nectar the bee is unable to harvest. In this dry climate it has been found that the pollen production has decreased which is essential in the honeybees diet. With a lack of pollen the bees can become deprived which would result in a weakened immune system, leaving them more susceptible to pathogens and viruses. If there is an increase in moisture, such as rain the flowers can get washed out which leaves them unattractive to bees (Le Conte and Navajas, 2008). While weather and climate affect the health of the honeybee it can also affect the areas available to the bees for building nests. A climate change can either increase or decrease an area available to a bee population. It has been found that bees will abandon areas that are prone to drought leaving them to migrate toward more moist environments. Although drastic changes may have negative effects on the bee populations they are able to adapt to different climates and environments over time. While the bees are able to adapt to new locations they have been found in highly diverse environments with a variety of different climates. Although CCD is one explanation for the drastic loss in colony numbers it is not the only factor to consider. Climate and weather can have similar affects on a colony that are also seen with CCD; these effects include loss of a colony or abandonment of a hive. Different migration rates of plants and insects resulting from climate change can affect the synchrony between the pollinators and flowering plants. This disruption can lead to spatial dislocation of pollination, which can have a negative effect on flowering plants and crops (Vanbergen et al, 2013). 7

8 Behavior CCD is not only affecting the honeybee population but also the behaviors exhibited by this organism. It has been observed that the adult bees divest the hive, not only leaving the queen behind but also the honey and pollen (Kribs-Zaleta et,al 2014). The honey that is left behind in the abandoned hive remains untouched by other honeybees. A proposed theory to explain this behavior is pathogens or contaminants encountered during foraging. According to Chensheng, Warchol and Callahan (2014), CCD is affecting another behavior in honeybees; it is affecting the winterization of healthy colonies. The result is at the end of winter bees are abandoning their hives and then dying. According to Rueppell, Hayworth and Ross (2010), when a bee is compromised by an illness it will depart from the hive in order to prevent spreading the infection to the rest of the hive. This may provide a possible explanation as to why honeybees abandon their hives when it is thought they have been affected by CCD. According to Henry et al, (2012), 10.2%-31.6% of honeybees that were exposed to sub-lethal amounts of neonicotinoid on a daily basis would fail to return to their colonies. There was a higher probability that the forager would die due to homing failure compared to forager bees that would die of natural causes. Exposure to a different, nonlethal pesticide thiamethoxam still affects foraging activity and has the potential to contribute to colony collapse. Forager survival is effected by exposure and the extent is dependent upon the landscape context and the knowledge that the foragers have on this particular landscape. Exposure to sub-lethal levels of fluvalinate, which is a chemical that is used to treat hives, preventing parasite infestation was found to affect feeding and navigation (Ho 8

9 and Cummins, 2007). Sub-lethal doses of a pesticide called fipronil were found to impair the olfactory memory process in the honeybee. Behavior can also be affected by the presence of a protozoan called Nosema caranae, which affects the hunger level of the bee, leading to a lower survival rate (Mayack and Naug, 2009). With this increase in hunger there is also a higher trophallactic rate, which can contribute to an increase in the transmission of pathogens within the colony. Riskier foraging done by bees that are in a lower energetic state due to infection of N. caranae could be contributing to the disappearance of bees because they are likely unable to make it back to their hives. US Agriculture Honeybees are one of the primary pollinators for a majority of the agricultural crops and wild plants in the United States. Pollinators in general are essential for global diversity; they are able to provide vital services to crops and wild plants. The honeybee has been documented to be able to increase yield in 96% of animal-pollinated crops (Potts et al, 2010). A decline in pollination due to the continuing loss of bee colonies would begin to affect the wild plant species, 80% of which are dependent on insect pollination for fruits and seeds. Plants that have a more specialized pollination requirement are thought to be at more risk although there is little evidence of a buffer system within the plant that allow for some loss of pollination. A large disturbance could cause a collapse in the plant-pollinator network, which would severely affect the agriculture that humans are so dependent on. Bees are responsible for roughly 75% of all the pollination required for human food worldwide. Fruit crops are a large proportion of the pollinated crops and are more 9

10 vulnerable to a decrease in pollination. Growers have been dependent on either renting honeybees or utilizing wild honeybees in order to pollinate their crops. Complete loss in pollination from honeybees shows a deficit that is over the present consumption levels (Potts et al, 2010). A compete loss of pollination from honeybees is a concern because the proportion of agricultural crops that are dependent on pollination are increasing at a rapid rate, increasing the demand for pollination. If CCD continues it has the potential to cause $15 billion loss in crop production (Kluser and Pascal 2007). With the continued decline in the honeybee population there would be a decrease in flower visitation, which can lead to abrupt or gradual decreases in seed and fruit production. CCD may not be the only contributing factor in the decrease of pollination by honeybees; land use can lead to eradication of a pollinating species both on local and regional scales (Vanbergen et al, 2013). Habitat fragmentation and degradation can contribute to a loss in pollination from the bee population. By removing habitats that are normally inhabited by honeybees there is a decreased probability that the bees will pollinate the plants nearby. Habitat fragmentation can affect large habitats and if there are a large number of small isolated patches the bee populations are likely to decline resulting in ineffective pollination (Kluser and Pascal 2007). Conclusion The causes of CCD remain a mystery but the harmful effect it has on the honeybee population is obvious. These harmful effects are causing dramatic decreases in worker bees during the winter months resulting in abandoned hives. It is unknown what 10

11 the main cause of this decrease is but it is thought to be a combination of many things that is causing death among bee colonies. Among the possible causes are things such as pathogens, pesticides, pests and viruses. Climate and weather are having a similar effect on the bee population and should be taken into consideration when exploring the loss of colonies. CCD is affecting honeybees worldwide, although the loss of honeybees appears to be less drastic in Europe compared to the United States. CCD is affecting behavior exhibited by the bee population in that their foraging behavior is being altered so intensely that some are unable to return to their hive. This altered behavior may provide an explanation as to why bees are abandoning their hives, when bees are infected with a pathogen or virus they leave the hive to prevent transmittance of infection. One of the major concerns relating to the decrease in colony numbers is its affect on US agriculture. Honeybees are one the main pollinators for the majority of the food found in a typical American home. A loss in honeybees means a decrease in pollination, which would ultimately affect crop production and a loss of millions of dollars. Although CCD may not be the only reason to explain the loss of honeybee colonies and the decrease in pollination it certainly is contributing to the problem. People are unaware of how important honeybees are to the ecosystem and if the decline continues there may be permanent damage that affects many species including our own. 11

12 References: Betti, B. I., W. M. Wahl, and M. Zamir. "Effects of Infection on Honey Bee Population Dynamics: A Model." PLOS One 9.10 (2014): Web. Boecking, O., and E. Genersch. "Varroosis-the Ongoing Crisis in Bee Keeping." Journal for Verbraucherschutz and Lebensmittelsicherheit-journal for Consumer Protection and Food Safety 3.2 (2008): Web. Chensheng, L., K. M. Warchol, and R. A. Callahan. "Sub-lethal Exposure to Neonicotinoids Impaired Honey Bess Winterization before Proceeding to Colony Collapse Disorder." Bullitin of Insectology 67.1 (2014): Web. Dainat, Benjamin, Dennis Vanengelsdorp, and Peter Neumann. "Colony Collapse Disorder in Europe." Environmental Microbiology Reports 4.1 (2012): Web. Dainat, B., J. D. Evans, Y. P. Chen, L. Gauthier, and P. Neumann. "Dead or Alive: Deformed Wing Virus and Varroa Destructor Reduce the Life Span of Winter Honeybees." Applied and Environmental Microbiology 78.4 (2012): Web. Henry, M., M. Beguin, F. Requier, O. Rollin, J.-F. Odoux, P. Aupinel, J. Aptel, S. Tchamitchian, and A. Decourtye. "Response to Comment on "A Common Pesticide Decreases Foraging Success and Survival in Honey Bees"" Science (2012): Web. Ho, M. W., and J. Cummins. "Mystery of Disappearing Honeybees." Science in Society 34 (2007): Web. Kluser, S., and P. Peduzzi. "Global Pollinator Decline: A Literature Review." United Nations Environment Programme (2007): n. pag. Web. Kribs-Zaleta, C. M., and C. M. Mitchell. "Modeling Colony Collapse Disorder in Honeybees as a Contagion." Mathmatical Biosciences and Engineering 11.6 (2014): Web. Le Conte, Y., and M. Navajas. "Climate Change: Impact on Honey Bee Populations and Diseases." Revue Scientifique Et Technique-office International Des Epizooties 27.2 (2008): Web. Mayack, Christopher, and Dhruba Naug. "Energetic Stress in the Honeybee Apis Mellifera from Nosema Ceranae Infection." Journal of Invertebrate Pathology (2009): Web. Potts, Simon G., Jacobus C. Biesmeijer, Claire Kremen, Peter Neumann, Oliver Schweiger, and William E. Kunin. "Global Pollinator Declines: Trends, Impacts and Drivers." Trends in Ecology & Evolution 25.6 (2010): Web. Rueppell, O., M. K. Hayworth, and N. P. Ross. "Altruistic Self-removal of Healthcompromised Honey Bee Workers from Their Hive." Journal of Evolutionary Biology 23.7 (2010): Web. Ryabov, E. V., G. R. Wood, J. M. Fannon, J. D. Moore, J. C. Bull, D. Chandler, A. Mead, N. Burroughs, and D. J. Evans. "A Virulent Strain of Deformed Wing Virus (DWV) of Honeybees (Apis Mellifera) Prevails after Varroa Destructor- Mediated, or In Vitro, Transmission." PLOS One 10.6 (2014): Web. 12

13 Sandrock, C., M. Tanadini, L. G. Tanadini, A. Fauser-Misslin, S. G. Potts, and P. Neumann. "Impact of Chronic Neonicotinoid Exposure on Honeybee Colony Performance and Queen Supersedure." PLOS One 9.8 (2014): Web. Sluijs, Jeroen P Van Der, Noa Simon-Delso, Dave Goulson, Laura Maxim, Jean-Marc Bonmatin, and Luc P. Belzunces. "Neonicotinoids, Bee Disorders and the Sustainability of Pollinator Services." Current Opinion in Environmental Sustainability (2013): Web. Smith, K. M., E. H. Loh, M. K. Rostal, C. M. Zambrana-Torrelio, L. Mendiola, and P. Daszak. "Pathogens, Pests, and Economics: Drivers of Honey Bee Colony Declines and Losses." Ecohealth 10.4 (2013): Web. Vanbergen, Adam J., and The Insect Pollinators Initiative. "Threats to an Ecosystem Service: Pressures on Pollinators." Frontiers in Ecology and the Environment 11.5 (2013): Web. Vanengelsdorp, Dennis, and Marina Doris Meixner. "A Historical Review of Managed Honey Bee Populations in Europe and the United States and the Factors That May Affect Them." Journal of Invertebrate Pathology 103 (2010): S Web. Vanengelsdorp, Dennis, Jay D. Evans, Claude Saegerman, Chris Mullin, Eric Haubruge, Bach Kim Nguyen, Maryann Frazier, Jim Frazier, Diana Cox-Foster, Yanping Chen, Robyn Underwood, David R. Tarpy, and Jeffery S. Pettis. "Colony Collapse Disorder: A Descriptive Study." Ed. Justin Brown. PLoS ONE 4.8 (2009): E6481. Web. 13

Bees. By: Jourdan Wu, Olakunle Olawonyi, Adina Gibson, Elizabeth Peterson. Image drawn by Adina Gibson using Sketchpad 5.1

Bees. By: Jourdan Wu, Olakunle Olawonyi, Adina Gibson, Elizabeth Peterson. Image drawn by Adina Gibson using Sketchpad 5.1 Bees By: Jourdan Wu, Olakunle Olawonyi, Adina Gibson, Elizabeth Peterson Image drawn by Adina Gibson using Sketchpad 5.1 According to an Article by NRDC (Natural Resources Defense Council) titled Why We