Colony collapse disorder (CCD) is a phenomenon in which worker bees from a beehive or European honey bee colony abruptly disappear. While such disappearances have occurred throughout the history of apiculture, and were known by various names (disappearing disease, spring dwindle, May disease, autumn collapse, and fall dwindle disease), the syndrome was renamed colony collapse disorder in late 2006 in conjunction with a drastic rise in the number of disappearances of Western honeybee colonies in North America. European beekeepers observed similar phenomena in Belgium, France, the Netherlands, Greece, Italy, Portugal, and Spain, and initial reports have also come in from Switzerland and Germany, albeit to a lesser degree while the Northern Ireland Assembly received reports of a decline greater than 50%.
The growth in the use of neonicotinoid pesticides such as acetamiprid, clothianidin and imidacloprid, some of the most widely-used pesticides in the world, has roughly tracked rising bee deaths since 2005. In 2012, several peer reviewed independent studies were published showing that neonicotinoids had previously undetected routes of exposure affecting bees including through dust, pollen, and nectar; that sub-nanogram toxicity resulted in failure to return to the hive without immediate lethality, the primary symptom of CCD, and indicating environmental persistence of neonicotinoids in irrigation channels and soil. These studies prompted a formal 2013 peer review by the European Food Safety Authority that said neonicotinoids pose an unacceptably high risk to bees, and that the industry-sponsored science upon which regulatory agencies' claims of safety have relied is flawed. CCD is probably compounded by a combination of factors. In 2007, some authorities attributed the problem to biotic factors such as Varroa mites, Nosema apis parasites, and Israel acute paralysis virus. Other contributing factors may include environmental change-related stress, malnutrition, and migratory beekeeping. Another study in 2012 also pointed to multiple causes, listing pesticides behind the varroa mite, genetics, habitat loss, and poor nutrition.
Colony collapse is significant economically because many agricultural crops worldwide are pollinated by European honey bees. In April 2013, the European Union announced plans to restrict the use of certain pesticides to stop bee populations from declining further and by the end of the month passed legislation which banned the use of several neonicotinoids for the following two years. Shortages of bees in the US have increased the cost to farmers of renting them for pollination services by up to 20%.
Limited occurrences resembling CCD have been documented as early as 1869 and this set of symptoms has, in the past several decades, been given many different names (disappearing disease, spring dwindle, May disease, autumn collapse, and fall dwindle disease). Most recently, a similar phenomenon in the winter of 2004/2005 occurred, and was attributed to Varroa mites (the "Vampire Mite" scare), though this was never ultimately confirmed. The cause of the appearance of this syndrome has never been determined. Upon recognition that the syndrome does not seem to be seasonally restricted, and that it may not be a "disease" in the standard sense—that there may not be a specific causative agent—the syndrome was renamed.
There was a well documented outbreak of colony losses spreading from the Isle of Wight to the rest of the UK in 1906. These losses later were attributed to a combination of factors including adverse weather, intensive apiculture leading to inadequate forage, and a new infection, the chronic bee paralysis virus;  but, at the time, the cause of this agricultural beekeeping problem was similarly mysterious and unknown.
Reports show this 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 there were few or no bees, discrediting reports that attributed the disappearances to lack of food.
From 1972 to 2006, dramatic reductions continued in the number of feral honey bees in the U.S. and a significant though somewhat gradual decline in the number of colonies maintained by beekeepers. This decline includes the cumulative losses from all factors, such as 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 the term "colony collapse disorder" began to be used to describe this sudden rash of disappearances (sometimes referred to as Spontaneous Hive Collapse or the Mary Celeste Syndrome in the United Kingdom).
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. The first report of CCD was in mid-November 2006 by a Pennsylvania beekeeper overwintering in Florida. By February 2007, large commercial migratory beekeepers in several states 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 loss of nearly all of their colonies with surviving colonies so weakened that they might no longer be viable to pollinate or produce honey.
Losses were reported in migratory operations wintering in California, Florida, Oklahoma, and Texas. In late February, some larger non-migratory beekeepers in the mid-Atlantic and Pacific Northwest regions also reported significant losses of more than 50%. Colony losses also were reported in five Canadian provinces, several European countries, and countries in South and Central America and Asia. In 2010, the USDA reported that data on overall honey bee losses for 2010 indicated an estimated 34 percent loss, which is statistically similar to losses reported in 2007, 2008, and 2009.
Signs and symptoms
A colony which has collapsed from CCD is generally characterized by all of these conditions occurring simultaneously:
Presence of capped brood in abandoned colonies. Bees normally will not abandon a hive until the capped brood have all hatched.
Presence of food stores, both honey and bee pollen:
i. which are not immediately robbed by other bees
ii. which when attacked by hive pests such as wax moth and small hive beetle, the attack is noticeably delayed.
Presence of the queen bee. If the queen is not present, the hive died because it was queenless, which is not considered CCD.
Precursor symptoms that may arise before the final colony collapse are:
Insufficient workforce to maintain the brood that is present
Workforce seems to be made up of young adult bees
The colony members are reluctant to consume provided feed, such as sugar syrup and protein supplement.
Scope and distribution
The National Agriculture Statistics Service reported that there were 2.44 million honey-producing hives in the United States as of February 2008, down from 4.5 million in 1980, and 5.9 million in 1947, though these numbers underestimate the total number of managed hives as they exclude several thousand hives managed for pollination contracts only, and also do not include hives managed by beekeepers owning fewer than 5 hives. This under-representation may be offset by the practice of counting some hives more than once; hives that are moved to different states to produce honey are counted in each state's total and summed in total counts.
Non-CCD winter losses as high as 50% have occurred in some years and regions (e.g., 2000–2001 in Pennsylvania). Normal winter losses are typically considered to be in the range of 15–25%. In many cases, beekeepers reporting significant losses of bees did not experience true CCD, but losses due to other causes.
In 2007 in the US, at least 24 different states as well as portions of Canada had reported at least one case of CCD. In a 2007 survey of 384 responding beekeepers from 13 states, 23.8% met the specified criterion for CCD (that 50% or more of their dead colonies were found without bees and/or with very few dead bees in the hive or apiary).
In the US in 2006–2007, CCD-suffering operations had a total loss of 45% compared to the total loss of 25% of all colonies experienced by non-CCD suffering beekeepers.
A 2007–2008 survey of over 19% of all colonies revealed a total loss of 35.8%. Operations that pollinated almonds lost, on average, the same number of colonies as those that did not. The 37.9% of operations that reported having at least some of their colonies die with a complete lack of bees had a total loss of 40.8% of colonies compared to the 17.1% loss reported by beekeepers without this symptom. Large operations were more likely to have this symptom suggesting that a contagious condition may be a causal factor. Sixty percent of all colonies that were reported dead in this survey died without the presence of dead bees in the hive, and thus possibly suffered from CCD.
In 2010, the USDA reported that data on overall honey bee losses for the year indicate an estimated 34% loss, which is statistically similar to losses reported in 2007, 2008, and 2009. In 2011, the loss was 30%. In 2012–2013, CCD was blamed for the loss of about half of the US honeybee hives, far more than the 33% losses observed on average over previous years.
According to the European Food Safety Authority (EFSA), in 2007 the United Kingdom had 274,000 hives, Italy had 1,091,630, and France 1,283,810. In 2008, the British Bee Keepers Association reported that the bee population in the United Kingdom dropped by around 30% between 2007 and 2008, and an EFSA study revealed that in Italy the mortality rate was 40–50%. However, EFSA officials point out that the figures are not very reliable because before the bees started dying there was no harmonisation in the way different countries collected statistics on their bee populations. At that time (2008) the reports blamed the high death rate on the varroa mite, two seasons of unusually wet European summers, and some pesticides.
In 2010, David Aston of the British Beekeepers’ Association stated, "We still do not believe CCD (which is now better defined) is a cause of colony losses in the UK, however we are continuing to experience colony losses, many if not most of which can be explained". He feels that recent studies suggest "further evidence to the evolving picture that there are complex interactions taking place between a number of factors, pathogens, environmental, beekeeping practices and other stressors, which are causing honey bee losses described as CCD in the US".
In 2009, Tim Lovett, president of the British Beekeepers' Association, said: "Anecdotally, it is hugely variable. There are reports of some beekeepers losing almost a third of their hives and others losing none. John Chapple, chairman of the London Beekeepers' Association, put losses among his 150 members at between a fifth and a quarter. "There are still a lot of mysterious disappearances; we are no nearer to knowing what is causing them." The government's National Bee Unit continued to deny the existence of CCD in Britain; it attributes the heavy losses to the varroa mite and rainy summers that stop bees foraging for food.
Bee keepers in Scotland also reported losses for the past three years. Andrew Scarlett, a Perthshire-based bee farmer and honey packer, lost 80% of his 1,200 hives during the 2009 winter. He attributed the losses to a virulent bacterial infection that quickly spread because of a lack of bee inspectors, coupled with sustained poor weather that prevented honeybees from building up sufficient pollen and nectar stores.
In Germany, where some of the first reports of CCD in Europe appeared, and where, according to the German national association of beekeepers, 40% of the honey bee colonies died, there was no scientific confirmation; as of early May 2007, the German media were reporting that no confirmed CCD cases seemed to have occurred in Germany.
At the end of May 2012, the Swiss government reported that about half of the bee population had not survived the winter. The main cause of the decline was thought to be the parasite Varroa destructor.
The mechanisms of CCD are still unknown, but many causes have been proposed as causative agents: malnutrition, pathogens, immunodeficiencies, mites, fungus, pesticides, beekeeping practices (such as the use of antibiotics, or long-distance transportation of beehives) and electromagnetic radiation. Whether any single factor or a combination of factors (acting independently in different areas affected by CCD, or acting in tandem) is responsible is still unknown; however most recent information suggests a combination of factors is most likely. It is likewise still uncertain whether CCD is a genuinely new phenomenon as opposed to a known phenomenon that previously only had a minor impact.
At present, the primary source of information, and the presumed "lead" group investigating the phenomenon, is the Colony Collapse Disorder Working Group, based primarily at Pennsylvania State University. Their preliminary report pointed out some patterns but drew no strong conclusions. A survey of beekeepers early in 2007 indicated that most hobbyist beekeepers believed that starvation was the leading cause of death in their colonies while commercial beekeepers overwhelmingly believed that invertebrate pests (Varroa mites, honey bee tracheal mites, and/or small hive beetles) were the leading cause of colony mortality. A scholarly review in June 2007 similarly addressed numerous theories and possible contributing factor, but left the issue unresolved.
In July 2007, the United States Department of Agriculture (USDA) released its "CCD Action Plan", which outlined a strategy for addressing CCD consisting of four main components:
1) survey and data collection;
2) analysis of samples;
3) hypothesis-driven research; and
4) mitigation and preventive action.
In July 2009, the first annual report of the U.S. Colony Collapse Disorder Steering Committee was published. It suggested that colony collapse may be caused by the interaction of many agents in combination.
Similarly, in 2009 the CCD Working Group published a comprehensive descriptive study that concluded: "Of the 61 variables quantified (including adult bee physiology, pathogen loads, and pesticide levels), no single factor was found with enough consistency to suggest one causal agent. Bees in CCD colonies had higher pathogen loads and were co-infected with more pathogens than control populations, suggesting either greater pathogen exposure or reduced defenses in CCD bees."
The second annual Steering Committee report was released in November 2010. The group reported that although many associations, including pesticides, parasites, and pathogens have been identified throughout the course of research, "it is becoming increasingly clear that no single factor alone is responsible for [CCD]". Their findings indicated an absence of damaging levels of the parasite Nosema or parasitic Varroa mites at the time of collapse.
They did find an association of sub-lethal effects of some pesticides with CCD, including two common miticides in particular, coumaphos and fluvalinate, which are pesticides registered for use by beekeepers to control varroa mites. It was reported that studies also identified sub-lethal effects of neo-nicotinoids and fungicides, pesticides that may impair the bee's immune system. It is hypothesized that these pesticides impair the bee's immune system, which leaves the bee more susceptible to bee viruses.
A large 2010 survey of healthy and CCD-affected colonies also revealed elevated levels of pesticides in wax and pollen, but the amounts of pesticides were similar in both failing and healthy hives. They also confirmed suspected links between CCD and poor colony health, inadequate diet, and long-distance transportation. Studies continue to show very high levels of pathogens in CCD-affected samples and lower pathogen levels in non-affected samples, consistent with the empirical observation that healthy honey bee colonies normally fend off pathogens. These observations have led to the hypothesis that bee declines are resulting from immune suppression.
In the 29 March 2012, issue of the journal Science, two separate studies found that neonicotinoids (insecticides) may interfere with bee's natural homing abilities, causing them to become disoriented and preventing them from finding their way back to the hive.
European Food Safety Authority statement
In 2012, several peer reviewed independent studies were published showing that neonicotinoids had previously undetected routes of exposure affecting bees including through dust, pollen, and nectar and that sub-nanogram toxicity resulted in failure to return to the hive without immediate lethality, the primary symptom of CCD.
Research also showed environmental persistence in agricultural irrigation channels and soil. These reports prompted a formal peer review by the European Food Safety Authority, which stated in January 2013 that some neonicotinoids pose an unacceptably high risk to bees, and that the industry-sponsored science upon which regulatory agencies' claims of safety have relied on may be flawed and contain several data gaps not previously considered. Their review concluded, "A high acute risk to honey bees was identified from exposure via dust drift for the seed treatment uses in maize, oilseed rape and cereals. A high acute risk was also identified from exposure via residues in nectar and/or pollen." David Goulson, an author of one of the studies which prompted the EFSA review, has suggested that industry science pertaining to neonicotinoids may have been deliberately deceptive, and the UK Parliament has asked manufacturer Bayer Cropscience to explain discrepancies in evidence they have submitted to an investigation.
Further information: Pesticide toxicity to bees, Imidacloprid effects on bee population, and Bees and toxic chemicals
According to the U.S. Department of Agriculture, pesticides may be contributing to CCD. Scientists have long been concerned that pesticides and possibly some fungicides may have sub-lethal effects on bees, not killing them outright but instead impairing their development and behavior. Of special interest is the class of insecticides called neonicotinoids, which contain the active ingredient imidacloprid, and similar other chemicals, such as clothianidin and thiamethoxam. Honey bees may be affected by such chemicals when they are used as a seed treatment because they are known to work their way through the plant up into the flowers and leave residues in the nectar. Scientists note that the doses taken up by bees are not lethal, but they are concerned about possible chronic problems caused by long-term exposure. Virtually all of the genetically engineered Bt corn grown in the U.S. is treated with neonicoticoids and a 2012 study found high levels of clothianidin in pneumatic planter exhaust. In the study, it was found that the insecticide was present in the soil of unplanted fields nearby those planted with Bt corn and on dandelions growing near those fields. Another 2012 study done in Italy also found clothianidin and imidacloprid in the exhaust of pneumatic seeding equipment.
A 2010 survey reported 98 pesticides and metabolites detected in aggregate concentrations up to 214 ppm in bee pollen – this figure represents over half of the individual pesticide incidences ever reported for apiaries. It was suggested that "while exposure to many of these neurotoxicants elicits acute and sublethal reductions in honey bee fitness, the effects of these materials in combinations and their direct association with CCD or declining bee health remains to be determined."
It is particularly difficult to evaluate pesticide contributions to CCD for several reasons. First, the variety of pesticides in use in the different areas reporting CCD makes it difficult to test for all possible pesticides simultaneously. Second, many commercial beekeeping operations are mobile, transporting hives over large geographic distances over the course of a season, potentially exposing the colonies to different pesticides at each location. Third, the bees themselves place pollen and honey into long-term storage, effectively meaning that there may be a delay of anywhere from days to months before contaminated provisions are fed to the colony, negating any attempts to associate the appearance of symptoms with the actual time at which exposure to pesticides occurred.
Pesticides used on bee forage are far more likely to enter the colony via the pollen stores rather than via nectar (because pollen is carried externally on the bees, while nectar is carried internally, and may kill the bee if too toxic), though not all potentially lethal chemicals, either natural or man-made, affect the adult bees: many primarily affect the brood, but brood die-off does not appear to be happening in CCD. Most significantly, brood are not fed honey, and adult bees consume relatively little pollen; accordingly, the pattern in CCD suggests that if contaminants or toxins from the environment are responsible, it is most likely to be via the honey, as it is the adults that are dying (or leaving), not the brood (though possibly effects of contaminated pollen consumed by juveniles may only show after they have developed into adults).
To date, most of the evaluation of possible roles of pesticides in CCD have relied on the use of surveys submitted by beekeepers, but it seems likely that direct testing of samples from affected colonies will be needed, especially given the possible role of systemic insecticides such as the neonicotinoid imidacloprid (which are applied to the soil and taken up into the plant's tissues, including pollen and nectar), which may be applied to a crop when the beekeeper is not present. The known effects of imidacloprid on insects, including honey bees, are consistent with the symptoms of CCD; for example, the effects of imidacloprid on termites include apparent failure of the immune system, and disorientation.
In Europe, the interaction of the phenomenon of "dying bees" with imidacloprid has been discussed for quite some time now. It was a study from the "Comité Scientifique et Technique (CST)" which was in the center of discussion, which led to a partial ban of imidacloprid in France. The imidacloprid pesticide Gaucho was banned, in 1999 by the French Minister of Agriculture Jean Glavany, primarily due to concern over potential effects on honey bees. Consequently when fipronil, a phenylpyrazole insecticide and in Europe mainly labeled "Regent", was used as a replacement, it was also found to be toxic to bees, and banned partially in France in 2004.
In February 2007, about forty French deputies, led by UMP member Jacques Remiller, requested the creation of a Parliamentary Investigation Commission on Overmortality of Bees, underlining that honey production was decreasing by 1,000 tons a year for a decade. As of August 2007, no investigations were yet opened. Five other insecticides based on fipronil were also accused of killing bees. However, the scientific committees of the European Union are still of the opinion "that the available monitoring studies were mainly performed in France and EU-member-states should consider the relevance of these studies for the circumstances in their country".
Around the same time, French beekeepers succeeded in banning neonicotinoids, the Clinton administration permitted pesticides which were previously banned, including imidacloprid. In 2004, the Bush Administration reduced regulations further and pesticide applications increased.
In 2005, a team of scientists led by the National Institute of Beekeeping in Bologna, Italy, found pollen obtained from seeds dressed with imidacloprid contains significant levels of the insecticide, and suggested the polluted pollen might cause honey bee colony death. Analysis of maize and sunflower crops originating from seeds dressed with imidacloprid suggest large amounts of the insecticide will be carried back to honey bee colonies. Sublethal doses of imidacloprid in sucrose solution have also been documented to affect homing and foraging activity of honey bees. Imidacloprid in sucrose solution fed to bees in the laboratory impaired their communication for a few hours. Sublethal doses of imidacloprid in laboratory and field experiment decreased flight activity and olfactory discrimination, and olfactory learning performance was impaired.
Research, in 2008, by scientists from Pennsylvania State University found high levels of the pesticides fluvalinate and coumaphos in samples of wax from hives, as well as lower levels of 70 other pesticides. These chemicals have been used to try to eradicate varroa mites, a bee pest that itself has been thought to be a cause of CCD. Researchers from Washington State University, under entomology professor Steve Sheppard in 2009, confirmed high levels of pesticide residue in hive wax and found an association between it and significantly reduced bee longevity.
The WSU work also focused on the impact of the microsporidian pathogen Nosema ceranae, the build-up of which was high in the majority of the bees tested, even after large doses of the antibiotic fumagillin. Penn State's Dr. Maryann Frazier said, "Pesticides alone have not shown they are the cause of CCD. We believe that it is a combination of a variety of factors, possibly including mites, viruses and pesticides."
In 2010, Fipronil was blamed for the spread of colony collapse disorder among bees, in a study by the Minutes-Association for Technical Coordination Fund in France, which found that even at very low nonlethal doses, this pesticide still impairs the ability to locate the hive, resulting in large numbers of foragers lost with every pollen-finding expedition, though no mention was made regarding any of the other symptoms of CCD; other studies, however, have shown no acute effect of Fipronil on honey bees. Fipronil is designed to eliminate insects similar to bees, such as yellowjackets (Vespula germanica) and many other colonial pests by a process of toxic baiting, whereby one insect returning to the hive spreads the pesticide among the brood.
In 2012, researchers announced findings that sublethal exposure to imidacloprid rendered honey bees significantly more susceptible to infection by the fungus Nosema, thereby suggesting a potential link to CCD, given that Nosema is increasingly considered to contribute to CCD.
Also, in 2012, researchers in Italy published findings that the pneumatic drilling machines that plant corn seeds coated with clothianidin and imidacloprid release large amounts of the pesticide into the air, causing significant mortality in foraging honey bees. According to the study, "Experimental results show that the environmental release of particles containing neonicotinoids can produce high exposure levels for bees, with lethal effects compatible with colony losses phenomena observed by beekeepers." Commonly used pesticides, such as the neonicotinoid imidacloprid reduce colony growth and new queen production in experimental exposure matched to field levels. Lu et al. (2012) reported they were able to replicate CCD with imidacloprid. Another neonicotinoid thiamethoxam causes navigational homing failure of foraging bees, with high mortality.
A 2012 in situ study provided strong evidence that exposure to sub-lethal levels of imidacloprid in high fructose corn syrup (HFCS) used to feed honey bees when forage is not available causes bees to exhibit symptoms consistent to CCD 23 weeks post imidacloprid dosing. The researchers suggested that "the observed delayed mortality in honey bees caused by imidacloprid in HFCS is a novel and plausible mechanism for CCD, and should be validated in future studies".
In March 2013, two studies were published showing that neonicotinoids affect bee long term and short term memory, suggesting a cause of action resulting in failure to return to the hive. Growth in the use of neonicotinoid pesticides has roughly tracked rising bee deaths.
Neonicotinoids banned by European Union
Early in 2013, the European Food Safety Authority issued a declaration that three specific neonicotinoid pesticides pose an acute risk to honeybees, and the European Commission (EC) proposed a two-year ban on them. David Goulson, who led one of the key 2012 studies at the University of Stirling said that the decision "begs the question of what was going on when these chemicals were first approved." The chemical manufacturer Bayer said it was "ready to work with" the EC and member states. In April 2013, the European Union voted for a two-year restriction on neonicotinoid insecticides. The ban will restrict the use of imidacloprid, clothianidin, and thiamethoxam for use on crops that are attractive to bees. Eight nations voted against the motion, including the British government which argued that the science was incomplete.
As we’ve written before, the mysterious mass die-off of honey bees that pollinate $30 billion worth of crops in the US has so decimated America’s apis mellifera population that one bad winter could leave fields fallow. Now, a new study has pinpointed some of the probable causes of bee deaths and the rather scary results show that averting beemageddon will be much more difficult than previously thought.
Scientists had struggled to find the trigger for so-called Colony Collapse Disorder (CCD) that has wiped out an estimated 10 million beehives, worth $2 billion, over the past six years. Suspects have included pesticides, disease-bearing parasites and poor nutrition. But in a first-of-its-kind study published today in the journal PLOS ONE, scientists at the University of Maryland and the US Department of Agriculture have identified a witch’s brew of pesticides and fungicides contaminating pollen that bees collect to feed their hives. The findings break new ground on why large numbers of bees are dying though they do not identify the specific cause of CCD, where an entire beehive dies at once.
When researchers collected pollen from hives on the east coast pollinating cranberry, watermelon and other crops and fed it to healthy bees, those bees showed a significant decline in their ability to resist infection by a parasite called Nosema ceranae. The parasite has been implicated in Colony Collapse Disorder though scientists took pains to point out that their findings do not directly link the pesticides to CCD. The pollen was contaminated on average with nine different pesticides and fungicides though scientists discovered 21 agricultural chemicals in one sample. Scientists identified eight ag chemicals associated with increased risk of infection by the parasite.
Most disturbing, bees that ate pollen contaminated with fungicides were three times as likely to be infected by the parasite. Widely used, fungicides had been thought to be harmless for bees as they’re designed to kill fungus, not insects, on crops like apples.
“There’s growing evidence that fungicides may be affecting the bees on their own and I think what it highlights is a need to reassess how we label these agricultural chemicals,” Dennis vanEngelsdorp, the study’s lead author, told Quartz.
Labels on pesticides warn farmers not to spray when pollinating bees are in the vicinity but such precautions have not applied to fungicides.
Bee populations are so low in the US that it now takes 60% of the country’s surviving colonies just to pollinate one California crop, almonds. And that’s not just a west coast problem—California supplies 80% of the world’s almonds, a market worth $4 billion.
In recent years, a class of chemicals called neonicotinoids has been linked to bee deaths and in April regulators banned the use of the pesticide for two years in Europe where bee populations have also plummeted. But vanEngelsdorp, an assistant research scientist at the University of Maryland, says the new study shows that the interaction of multiple pesticides is affecting bee health.
“The pesticide issue in itself is much more complex than we have led to be believe,” he says. “It’s a lot more complicated than just one product, which means of course the solution does not lie in just banning one class of product.”
The study found another complication in efforts to save the bees: US honey bees, which are descendants of European bees, do not bring home pollen from native North American crops but collect bee chow from nearby weeds and wildflowers. That pollen, however, was also contaminated with pesticides even though those plants were not the target of spraying.
“It’s not clear whether the pesticides are drifting over to those plants but we need take a new look at agricultural spraying practices,” says vanEngelsdorp.
For immediate release: May 9, 2014
Boston, MA — Two widely used neonicotinoids—a class of insecticide—appear to significantly harm honey bee colonies over the winter, particularly during colder winters, according to a new study from Harvard School of Public Health (HSPH). The study replicated a 2012 finding from the same research group that found a link between low doses of imidacloprid and Colony Collapse Disorder (CCD), in which bees abandon their hives over the winter and eventually die. The new study also found that low doses of a second neonicotinoid, clothianidin, had the same negative effect.
Further, although other studies have suggested that CCD-related mortality in honey bee colonies may come from bees’ reduced resistance to mites or parasites as a result of exposure to pesticides, the new study found that bees in the hives exhibiting CCD had almost identical levels of pathogen infestation as a group of control hives, most of which survived the winter. This finding suggests that the neonicotinoids are causing some other kind of biological mechanism in bees that in turn leads to CCD.
The study appears online May 9, 2014 in the Bulletin of Insectology.
“We demonstrated again in this study that neonicotinoids are highly likely to be responsible for triggering CCD in honey bee hives that were healthy prior to the arrival of winter,” said lead author Chensheng (Alex) Lu, associate professor of environmental exposure biology at HSPH.
Since 2006, there have been significant losses of honey bees from CCD. Pinpointing the cause is crucial to mitigating this problem since bees are prime pollinators of roughly one-third of all crops worldwide. Experts have considered a number of possible causes, including pathogen infestation, beekeeping practices, and pesticide exposure. Recent findings, including a 2012 study by Lu and colleagues, suggest that CCD is related specifically to neonicotinoids, which may impair bees’ neurological functions. Imidacloprid and clothianidin both belong to this group.
Lu and his co-authors from the Worcester County Beekeepers Association studied the health of 18 bee colonies in three locations in central Massachusetts from October 2012 through April 2013. At each location, the researchers separated six colonies into three groups—one treated with imidacloprid, one with clothianidin, and one untreated.
There was a steady decline in the size of all the bee colonies through the beginning of winter—typical among hives during the colder months in New England. Beginning in January 2013, bee populations in the control colonies began to increase as expected, but populations in the neonicotinoid-treated hives continued to decline. By April 2013, 6 out of 12 of the neonicotinoid-treated colonies were lost, with abandoned hives that are typical of CCD. Only one of the control colonies was lost—thousands of dead bees were found inside the hive—with what appeared to be symptoms of a common intestinal parasite called Nosema ceranae.
While the 12 pesticide-treated hives in the current study experienced a 50% CCD mortality rate, the authors noted that, in their 2012 study, bees in pesticide-treated hives had a much higher CCD mortality rate—94%. That earlier bee die-off occurred during the particularly cold and prolonged winter of 2010-2011 in central Massachusetts, leading the authors to speculate that colder temperatures, in combination with neonicotinoids, may play a role in the severity of CCD.
“Although we have demonstrated the validity of the association between neonicotinoids and CCD in this study, future research could help elucidate the biological mechanism that is responsible for linking sub-lethal neonicotinoid exposures to CCD,” said Lu. “Hopefully we can reverse the continuing trend of honey bee loss.”
Funding for the study came from Wells Fargo Foundation and the Breck Fund at the Harvard University Center for the Environment.
“Sub-lethal exposure to neonicotinoids impaired honey bees winterization before proceeding to colony collapse disorder,” Chensheng Lu, Kenneth M. Warchol, Richard A. Callahan, Bulletin of Insectology, online Friday, May 9, 2014
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Feds: Many causes for dramatic bee disappearance
By SETH BORENSTEIN | Associated Press
WASHINGTON (AP) — A new federal report blames a combination of problems for a mysterious and dramatic disappearance of U.S. honeybees since 2006.
The intertwined factors cited include a parasitic mite, multiple viruses, bacteria, poor nutrition, genetics, habitat loss and pesticides.
The multiple causes make it harder to do something about what's called colony collapse disorder, experts say. The disorder has caused as much as one-third of the nation's bees to just disappear each winter since 2006.
Bees, especially honeybees, are needed to pollinate crops.
The federal report, issued Thursday by the Agriculture Department and the Environmental Protection Agency, said the biggest culprit is the parasitic mite varroa destructor, calling it "the single most detrimental pest of honeybees."
The problem has also hit bee colonies in Europe, where regulators are considering a ban on a type of pesticides known as neonicotinoids that some environmental groups blame for the bee collapse. The U.S. report cites pesticides, but near the bottom of the list of factors. And federal officials and researchers advising them said the science doesn't justify a ban of the pesticides yet.
May Berenbaum, a top bee researcher from the University of Illinois, said in an interview that she was "extremely dubious" that banning the pesticide would have any effect on bee health. She participated in a large conference of scientists that the government brought together last year to figure out what's going on, and the new report is the result of that conference.
Berenbaum said more than 100 different chemicals — not just the pesticides that may be banned in Europe — have been found in bee colonies. Scientists find it hard to calculate how they react in different dosages and at different combinations, she said.
Some of these chemicals harm the immune systems of bees or amplify viruses, said Penn State University bee expert Diana Cox-Foster.
At a news conference Thursday, Sonny Ramaswamy, a top USDA official, said the scientific consensus is that there are multiple factors "and you can't parse any one out to be the smoking gun."
USDA bee researcher Jeff Pettis also cited modern farming practices that often leave little forage area for bees.
Dave Gaulson of the University of Stirling in Scotland, who conducted a study last year that implicated the chemical, said he can't disagree with the overall conclusions of the U.S. government report. However, he said it could have emphasized pesticides more.
The environmental group, Pesticide Action Network North America blasted the federal government for not following Europe's lead in looking at a ban of certain pesticides.
Pollinators, like honeybees, are crucial to the U.S. food supply. About $30 billion a year in agriculture depends on their health, said Ramaswamy
Besides making honey, honeybees pollinate more than 90 flowering crops. Among them are a variety of fruits and vegetables: apples, nuts, avocados, soybeans, asparagus, broccoli, citrus fruit and cranberries. About one-third of the human diet comes from insect-pollinated plants, and the honeybee is responsible for 80 percent of that pollination.
"It affects virtually every American whether they realize it or not," said EPA acting administrator Bob Perciasepe.
Zac Browning, a fourth-generation commercial beekeeper who has hives in Idaho, North Dakota and California, said the nation is "on the brink" of not having enough bees to pollinate its crops.
University of Maryland entomologist David Inouye, who was not part of the federal report, said he agrees that there are multiple causes.
"It's not a simple situation. If it were one factor we would have identified it by now," he said.
Inouye, president-elect of the Ecological Society of America, said the problems in Europe and United States may be slightly different. In America, bee hives are trucked from farm to farm to pollinate large tracts of land and that may help spread the parasites and disease, as well as add stress to the colonies, while in Europe they stay put so those issues may not be as big a factor.
At the news conference, Berenbaum said there's no single solution to the U.S. bee problem: "We're not really well equipped or even used to fighting on multiple fronts."