Colony collapse disorder
Colony collapse disorder is an abnormal phenomenon that occurs when the majority of worker bees in a honey bee colony disappear, leaving behind a queen, plenty of food, and a few nurse bees to care for the remaining immature bees. While such disappearances have occurred sporadically throughout the history of apiculture, and have been known by various names, the syndrome was renamed colony collapse disorder in early 2007 in conjunction with a drastic rise in reports of disappearances of western honey bee colonies in North America. Beekeepers in most European countries had observed a similar phenomenon since 1998, especially in Southern and Western Europe; the Northern Ireland Assembly received reports of a decline greater than 50%. The phenomenon became more global when it affected some Asian and African countries as well. Despite that, from 1990 to 2021, the United Nation's FAO calculated that the worldwide number of honeybee colonies increased 47%, reaching 102 million.
Colony collapse disorder could cause significant economic losses because many agricultural crops worldwide depend on pollination by western honey bees. According to FAO, the total value of global crops pollinated by honey bees was estimated at nearly US$200 billion in 2005. In the United States, shortages of bees have increased the cost to farmers renting them for pollination services by up to 20%. Declining numbers of bees predate CCD by several decades, however: the US managed hive industry has been shrinking at a steady pace since 1961.
In contrast, the managed bee population worldwide has been increasing steadily since 1975 to serve honey production, with China responsible for most of the growth. The period with the lowest growth in worldwide honey production was between 1991 and 1999, because of the economic collapse after the dissolution of communism in the former Soviet sphere of influence., the production has increased further by 50% compared to 2000, double the rate of growth in previous decades, notwithstanding CCD. Experts estimate that there are currently more honey bees alive worldwide than at any other point in human history.
Several possible causes for CCD have been proposed, but no single proposal has gained widespread acceptance among the scientific community. Suggested causes include pesticides, infections with various pathogens, malnutrition, genetic factors, immunodeficiencies, loss of habitat, or changing beekeeping practices; combinations of these factors have also been cited. A large amount of speculation has surrounded the contributions of the neonicotinoid family of pesticides to CCD, but many collapsing apiaries show no trace of these chemicals.
History
Colony collapse disorder is a syndrome defined by a specific set of symptoms that was previously given many different names. The cause of these historic collapses has never been determined, but CCD has been described as "death by a thousand cuts with the most obvious one being Varroa". After it was recognized that the syndrome does not seem to be seasonally restricted and that it may not be a "disease" in the standard sense—there may not be one specific causative agent or pathogenesis—the syndrome was renamed in 2007.Limited occurrences resembling CCD were documented as early as 1869. Colony collapses were called "May Disease" in Colorado in 1891 and 1896.
A well-documented outbreak of colony losses spread from the Isle of Wight to the rest of the UK in 1906. These losses were later attributed to a combination of factors, including adverse weather, intensive apiculture leading to inadequate forage, Acarine mites, and a new infection, the chronic bee paralysis virus, but during the outbreak, the cause of this agricultural beekeeping problem was unknown.
Reports show similar behavior in hives in the US in 1918 and 1919. Coined "mystery disease" by some, it eventually became more widely known as "disappearing disease". Oertel, in 1965, reported that hives afflicted with disappearing disease in Louisiana had plenty of honey in the combs, although few or no bees were present, discrediting reports that attributed the disappearances to lack of food.
In the US, the number of colonies maintained by beekeepers has been in decline since the 1960s, for various reasons including urbanization, pesticide use, tracheal and Varroa mites, and commercial beekeepers retiring and going out of business. However, in late 2006 and early 2007, the rate of attrition was alleged to have reached new proportions, and people began to use the term colony collapse disorder to describe the sudden rash of disappearances.
Losses had remained stable since the 1990s at 17–20% per year, attributable to a variety of factors, such as mites, diseases, and management stress. In the winter of 2004–2005, a spontaneous collapse occurred and was attributed to varroa mites, though this was ultimately never confirmed. The first report classified as CCD was in mid-November 2006 by a Pennsylvania beekeeper overwintering in Florida. By February 2007, large commercial migratory beekeepers wintering in California, Florida, Oklahoma, and Texas had reported heavy losses associated with CCD. Their reports of losses varied widely, ranging from 30% to 90% of their bee colonies; in some cases, beekeepers reported losses of nearly all of their colonies, with surviving colonies so weakened that they might no longer be able to pollinate or produce honey. In late February 2007, some larger non-migratory beekeepers in the mid-Atlantic and Pacific Northwest regions also reported significant losses of more than 50%. Colony losses were also reported in five Canadian provinces, several European countries, and countries in South and Central America and Asia. In 2010, the United States Department of Agriculture reported that data on overall honey bee losses for 2010 indicated an estimated 34% loss, which is statistically similar to losses reported in 2007, 2008, and 2009. Fewer colony losses occurred in the US over the winter of 2013–2014 than in recent years. Total losses of managed honey bee colonies from all causes were 23.2% nationwide, a marked improvement over the 30.5% loss reported for the winter of 2012–2013 and the eight-year average loss of 29.6%.
After bee populations dropped 23% in the winter of 2013, the Environmental Protection Agency and Department of Agriculture formed a task force to address the issue. Since 2014, Congress has substantially subsidized the pollinator industry through the 2014 Farm Bill. The 2014 Farm Bill has allowed for up to $20 million worth of subsidies every fiscal year to be put toward conservation of honeybees, livestock, and farm-raised fish that suffer losses due to disease, weather events, or adverse conditions. In 2017, Congress implemented additional funding to protect bees from agricultural pesticide spray and dust applications while they are under contract to provide pollination services. The Agriculture Improvement Act of 2018, also known as the 2018 Farm Bill, increased the monetary cap for the annual financial aid for emergency assistance from $20 million to $34 million.
A survey by the University of Maryland and Auburn University published in 2023 found the number of United States honey bee colonies "remained relatively stable" although 48% of colonies were lost in the year that ended April 1, 2023, with a 12-year average annual mortality rate of 39.6%. The previous year the loss was 39% and the 2020–2021 loss was 50.8%. Beekeepers told the surveying scientists that a 21% loss over the winter is acceptable and more than three-fifths of beekeepers surveyed said their losses were higher than in 2022–2023.
In 2024, the United States Census of Agriculture reported an all-time high in commercial honey bee hives, making them the fastest-growing livestock segment in the country.
Signs and symptoms
CCD is not the same as colony decline which can be caused by various issues such as queen health, varroa mite infestation, nutrition, and various diseases. In collapsed colonies, CCD is suspected when it is observed that few adult bees are physically present in the colony. Unlike with other acute causes of die-off such as pesticide exposure, few if any dead bees are found in or near the hive, as if the hive had simply been abandoned. A colony that has collapsed from CCD is generally characterized by all of these conditions occurring simultaneously:- Presence of capped brood in abandoned colonies. Bees normally do not abandon a hive until the capped brood has all hatched.
- Presence of food stores, both honey and bee pollen:
- * that other bees do not rob immediately
- * with significantly delayed attacks by hive pests such as wax moths and small hive beetles
- Presence of the queen bee. If the queen is not present, the hive likely died because it was queenless, which is not considered CCD.
- No dead honey bee bodies present
- Inability to maintain current brood due to low workforce
- Colony includes mostly young adult bees
- Bees are reluctant to consume provided feed, such as sugar syrup and protein supplement.
Genetic and physio-pathological predictions
In addition, there are genetic indications in the gut that suggest the susceptibility of honey bees to CCD. Sixty-five different RNA transcripts have been determined as potential signs for CCD status. Genetic expression of these transcripts was either upregulated or downregulated depending on genes when comparing them to healthy bees. The abundance of unusual ribosomal RNA fragments containing poly-rich 3′ tails was detected via microarray analysis and qPCR in the guts of CCD bees. This evidence suggests that these poly-rRNA sequences play the role of degradation intermediates to help in protein folding and enzymatic activity of rRNA. Furthermore, the presence of deformed wing virus and Israeli acute paralysis virus as well as the expression of poly-rRNA are genetic indications for the appearance of CCD.