Honey bees are one of the most important insect species for our planet. This is because they are among the most important pollinators of food crops – without honey bees many plants cannot grow and multiply. However, there are many issues today that put honey bee populations at risk, including climate change, pesticide and parasites. In recent years, one specific phenomenon leading to the decline of honey bee populations has received a lot of media attention. It’s called colony collapse disorder.
What is colony collapse disorder? Colony collapse disorder refers to a phenomenon where the majority of worker bees leave the hive and disappear. What distinguishes the colony collapse disorder from other causes of colony loss is the fact that most worker bees simply disappear. But, they leave behind a healthy queen, the brood, plenty of food resources and a certain number of nurse bees to care for the developing offspring.
Although similar occurrences have happened in the past, the phenomenon got the name “colony collapse disorder” in 2006, when it started happening on a massive scale all around the world. What exactly is colony collapse disorder? What causes it? How dangerous it is for the global population of honeybees and for the stability of ecosystems? These are some of the questions we will try to answer today.
Colony Collapse Disorder: What is it?
There is a number of causes that can lead to the decline of honey bee colonies and large colony losses, some of which include destructive industrial agriculture and the use of pesticides that are harmful to bees. However, the fact that there are dead bees doesn’t necessary mean you’re dealing with the colony collapse disorder (CCD).
In fact, one of the characteristics of CCD is that there are usually very few dead bees found close to the hive.
There are a couple of other symptoms that characterize CCD, as opposed to other issues that lead to the death of a colony. First of all, there is always a living queen present in hives that have suffered from CCD. If there is no queen in the hive, this means that the worker bees have left because the colony was queenless. This is a common cause of colony loss, but it is not considered CCD. Moreover, when CCD occurs the hive is usually left with abundant food reserves. The larvae in capped cells are left intact too, and there is usually a number of nurse bees left to care for the developing larvae. However, the number of worker bees left inside the hive is too low which eventually leads to the death of the colony.
There are also some signs that can point to CCD before the phenomenon occurs. Two key indicators are:
- The hive contains mostly young adult bees.
- An inability to nurse the larvae to full health, which happens when there are not enough worker bees present to care for the brood.
The History of Colony Collapse Disorder
The story about what is now called colony collapse disorder started (more or less) in 2006. Namely, during the winter of 2006-2007, many beekeepers began reporting losing an unusually high number of colonies. These reports heightened concern about colony losses has started in North America, but similar occurrences have actually been noted across Europe, and even in some Asian and African countries. This is already more than 10 years ago, so what’s changed? At the time, CCD was thought to be a major threat to the survival of honey bees in general, but in recent years, the number of reported cases of CCD has declined significantly. However, CCD is still a problem and we still don’t have a complete answer as to what causes it.
With that being said, phenomena similar to CCD have occurred periodically throughout the history of beekeeping. Such occurrences have been labeled by various names, including disappearing disease, spring dwindle, May disease, autumn collapse, and fall dwindle disease. While reports of such phenomena often involved a degree of mystery, today we actually understand the causes quite well.
For example, a case of increased colony losses that happened in the UK as far back as 1906 was very well documented. The “mysterious” disease spread from the Isle of Wight to the rest of the UK, and was known at the time as the “Isle of Wight disease”. A couple of years after, the disease was attributed to a specific type of mite that attacks beehives. However, today, we know that the “epidemic” was actually caused by several different issues that had similar symptoms, including unusually adverse weather conditions.
What are the Causes of Colony Collapse Disorder?
When it comes to CCD, there is still no clear answer as to what causes it. We don’t know whether is a combination of factors, or something specific that causes the bees to disappear in such a way. However, the likeliest answer is that CCD is not a mystery disease. A more plausible explanation would be that the disappearances of bee colonies are connected to one or more harmful factors in the environment that we are already aware of. It can be argued that multiple factors are responsible for CCD and scientists have speculated quite a lot on the topic of what causes CCD. Here are some of the possible explanations.
Diseases and Parasites
There is a considerable number of diseases and parasites that attack honey bees, which are usually all too familiar to skilled beekeepers. However, these diseases usually have symptoms that differ quite a bit from the mysterious disappearances of bees that happen with CCD.
For example, there are two bacterial infections that frequently attack honey bees, but they actually affect the larvae and not the adult bees, which is exactly the opposite of what happens with CCD. Moreover, when a colony is infected with parasites there are usually clear signs that point to the infection, which is clearly not the case with CCD. Finally, there might be a chance that various viral infection can be a factor contributing to CCD, but it is still highly unlikely that this is the only cause.
Pesticides and Chemicals
Today, much of agricultural practices across the world involve the use of pesticides in various degrees. Many of these pesticides are harmful to honey bees. Where the crops depend on bee pollination, it is necessary to be very careful. However, when bees are poisoned by the chemicals used in agriculture, this is usually very obvious and dead bees can be easily seen.
On the other hand, new types of pesticides are constantly being developed and there is one specific type called neonicotinoids. It has been suggested that these chemicals can be harmful to the bees’ health, but not enough to kill them immediately. These could lead to symptoms such as CCD over time.
Agricultural and Beekeeping Practices
Finally, various changes in human practices can seriously affect the life cycle of honey bees. This does not concern only CCD, but might be helpful in explaining this phenomenon. This might involve the use of genetically modified crops, but also the fact that some beekeepers lease colonies to farmers for the pollination of crops. This kind of practice can cause nutritional stress to bees which might be one of the causes leading to CCD.
Colony Collapse Disorder: Final Thoughts
“The way humanity manages or mismanages its nature-based assets, including pollinators, will in part define our collective future in the 21st century.”Achim Steiner, UN Under-Secretary-General and UNEP Executive Director
The importance of honey bees, and bees in general, can not be overestimated. While the colony collapse disorder remains somewhat of a mysterious phenomenon, it is beyond doubt that human activities and development are putting honey bees in danger. Air pollution, pesticides, and many other factors can have a negative effect. What can we do about it? Every little step counts! Planting bee-friendly flowers in your garden and buying local honey are some of the easiest actions that can be taken to help honey bees, at least just a little bit.
What causes the decline of honey bee populations and colony loss?
Some of the major threats that honey bee colonies all around the world are dealing with include diseases, parasites, poor nutrition, but also human-related factors such as pollution and pesticides. Foraging bees also depend on the weather a lot. They cannot go out during rainy periods, and during this time they need to live off the food reserves stored in the hive. If there is not enough food, this leads to poor nutrition. Poorly fed bees are not healthy, and this makes them more susceptible to diseases.
What parasites and insects can be dangerous to honey bees?
Large hornets and some large dragonflies both feed on honey bees. Moreover, there is a considerable amount of parasites that can attack the beehive. These include Varroa mites, tracheal mites, wax moths, and bee lice. See our other article for more information: https://schoolofbees.com/do-bees-carry-diseases/
EPA: Colony Collapse Disorder
Barron, Andrew. 2015. Death of the bee hive: understanding the failure of an insect society
Klein, Simon. 2017. Ten years after the crisis, what is happening to the world’s bees?
McCarthy, Michael. 2011. Decline of honey bees now a global phenomenon, says United Nations
Oldroyd, Benjamin. 2007. What’s Killing American Honey Bees?