Colony Collapse Disorder and the Ever-Evolving Plight of the Honeybee

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Trucks carry honeybees from field to field as part of a commercial pollination operation.
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Both samples show larvae infected with European foulbrood; the yellow discoloration is a hallmark sign.
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One of the classic symptoms of Colony Collapse Disorder is the lack of sufficient worker bees to tend the existing brood, indicating sudden loss of adult bees. The above frames contain far too many brood cells for the remaining adult population.
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A Varroa destructor mite feeds on a honeybee. Varroa mites are still considered to be one of the most virulent threats to honeybee health, spreading a range of infections.

Summer months in the American countryside bring with them a number of reassuring sensations: sweltering heat offset by welcome storms; the clanking of bullfrogs in creeks and ponds; luminous songbirds flickering about in the treetops; and from field and hedgerow, coming and going with an earnest symmetry, the droning buzz of the industrious honeybee. From wild hives in hollow snags to the enormous amalgamated beehives veiled in netting and towed between orchards on the back of tractor-trailer rigs, the western honeybee (Apis mellifera), originally a native of Eurasia and northern Africa, is now as American as Honey Nut Cheerios. But this pretty little insect, long a critical component of the world’s agriculture, is today facing an existential threat that, if not addressed in the short-term, could result in catastrophic losses across the farming industry.

In late 2006, entomologists were alerted to a troubling phenomenon. Rural residents across the country were suddenly reporting emptied beehives. It was as if the hives’ workers were suddenly seized with an impulse to flee their sanctuary, leaving behind no trace or explanation for their absconding. The golden honey itself, raison d’être of the bees’ legendary industriousness, was often left behind, uneaten and unutilized in the comb. And on some occasions, even more precious components of their cooperative lifestyle were abandoned, including pupae and, incredibly, the unprotected queen herself, a heretical act of desertion unknown to occur among healthy bees. These symptoms stemming from a collection of causes soon became known as Colony Collapse Disorder (CCD), a symptomatic term that beekeepers define in multiple ways.

More importantly, something alarming was afoot, and as the vanishings spread like a shroud of silence over the continent’s farmland, agronomists became duly concerned. Without honeybee pollination, many of our most common crops would fail to fruit, leaving us without our melons and pumpkins, our peanuts and macadamias, our sunflowers, our onions, our avocadoes, apricots and almonds. Pollination by bees, or entomophily, had been taken for granted by humankind since the Neolithic Era more than 12,000 years ago. Now our dependable little allies were abandoning their posts, leaving growers with that uneasy feeling that comes before a storm.

What’s happening to our honeybees?

Investigators believe there are likely several factors at work behind the disappearance of our honeybees. According to the USDA-sponsored Report on the National Stakeholders Conference on Honey Bee Health released in May 2013, the parasitic mite Varroa destructor remains the most damaging pest infesting hives. Not only are these mites devastating to proper larvae development — female mites feed on adult bee hemoglyph (or “bee blood”) before climbing into pre-capped larval cells to reproduce — but their bites have also been linked to another honeybee threat: bacterial and viral infection. A bacterial disease known as European foulbrood is of particular concern. Transmitted both orally through food supply as well as through Varroa destructor bite wounds, European foulbrood is increasingly being found in larvae, which can ultimately lead to larval death in high concentrations. The Israeli acute paralysis virus, a known cause of bee death outside the hive, has also been linked to Varroa mite infestation.

But why are honeybees falling victim to these parasitic and pathogenic threats at a much higher rate than ever before? While there have been widespread instances of colony decline over the course of the last century (if not longer), the post-2006 decline is alarming. It has been estimated that the average loss of honeybee hives last winter alone reached almost 50 percent among U.S. beekeepers. It is unclear whether these deaths can accurately be attributed to “Colony Collapse Disorder” specifically, with many bees slowly perishing in the hive rather than failing to return, but this distinction is ultimately irrelevant in the face of significant and continued pollinator loss. Many researchers, like Dr. Dennis vanEngelsdorp of the University of Maryland, now believe the real culprit to be a combination of factors that systematically compromises bee immunity, likening the condition to the HIV virus in humans: “You don’t die of AIDS; you die of pneumonia or some other condition that hits when your immunity is down,” he said.

This reduced immunity has been on the academic research agenda for quite some time now, and again, many researchers point to a variety of potential sources. Malnutrition stemming from a scarcity of diverse foraging habitat is thought to play a significant part. It has been well established, for example, that colonies with access to the best pollens from a variety of healthy sources are much more resistant to disease than their poorly nourished counterparts. Such food sources, however, are in rather limited supply these days due to the widespread practice of monoculture agriculture, where bees repeatedly feed on the same commodity crop and then are shipped half way across the country to feast on the same. The common and prolific use of pesticides on these crops is also problematic, for samples from diseased hives exhibit a regular smorgasbord of different agricultural chemicals.

Making repeated headlines today, though, is one particular class of pesticide in the nicotine family: neonicotinoid pesticides. While the USDA’s Agricultural Research Service reports that “there have been no credible scientific findings relating neonicotinoid pesticides as a direct cause of CCD,” they have confirmed that “there may be sub-lethal impacts on honeybees.” Indeed, evidence that neonicotinoids contribute significantly to the honeybee plight is difficult to refute: Their widespread agricultural application beginning in the mid-2000s is seemingly parallel to when the bee demise began to take hold.

On March 21, 2013, a lawsuit was filed in federal court by a coalition led by the Center for Food Safety against the Environmental Protection Agency (EPA) for failure to preemptively avert the honeybee crisis by hustling an untested and essentially unknown pesticide onto the market.

Central to the lawsuit is the EPA’s practice of “conditional registration,” a provision of the Federal Insecticide, Fungicide and Rodenticide Act that allows the EPA to discretionally admit various biocides into the United States without having conducted the rigorous scientific analyses that would prove their safety and suitability for use by the public.

Paul Towers is with the Pesticide Action Network and one of the plaintiffs in the EPA suit. He says that conditional registration is at the heart of the issue, whether or not neonicotinoids are solely responsible for the demise of the honeybee.

“This loophole expedites commercialization by bypassing meaningful premarket review,” he says. “Since 2000, over two-thirds of pesticide products, including clothianidin and thiamethoxam (both neonicotinoids), have been brought to market as conditional registrations.”

In allowing this to happen, claim the plaintiffs, the EPA may have unintentionally paved the way for any number of harmful chemical compounds to work their way into hives across the country. With more than 17,000 pesticide products currently on the market, unforeseen compounds and unplanned exposure are inevitable, particularly when apparent oversights in the federal review structure continue to allow unexamined chemicals free reign over American farm country.

At the basic level, neonicotinoids are systemic pesticides that persist in the environment and have a neurotoxity that may have adverse effects on honeybees, ecosystems and people. The effect of neonics on the honeybee’s central nervous system and neural transmission mechanism may play a part in their seeming inability to return to the hive.

The heavy reliance on chemicals by modern American agriculture is also suspected in yet another threat to honeybees. Fungicides play an increasing role in modern farming, and a new study published in the scientific journal PLOS One indicates that these poisons are contributing to the honeybee collapse by heightening hives’ susceptibility to Nosema ceranae, a unicellular parasitic fungus previously known only in Asian honeybees. And its spores are resistant to hot temperatures: a tailor-made pathogen for our industrialized climate.

Nosema ceranae induces a susceptibility to toxins in bees, and a 2009 study published in the journal Environmental Microbiology determined that bees infected with N. ceranae succumb to pesticides at amounts 100 times lower than that needed to kill uninfected bees. Given the widespread use of pesticides today, it’s difficult to imagine anyplace that is not contaminated with at least a modicum of deadly chemicals; enough, it now seems, to push a hive over the edge.

Indeed, new research from Spain indicates that N. ceranae can sometimes cause the collapse of colonies entirely on its own; when combined with habitat loss and other pervasive stressors — chemical, parasitic and climatic — even the hardiest hives risk succumbing, victims of a multipronged onslaught that these doughty little animals are simply not equipped to survive.

Uncertain future

The honeybee, like the dog and the horse, has a destiny inextricably tied to that of ours, an interactive relationship that spans the history of agriculture and remains one of our most fundamental ties to another species. After thousands of years of cooperative existence, of soothing summer evenings in which farmers everywhere have contentedly observed the humming circuit running its course between flower and hive, hive and flower, the honeybee may have arrived at the end of its capacity to serve us.

We may have very well breached a generous contract after centuries of faithful performance, and across the world the fields are falling silent. Let us hope we can find a solution before it’s too late.

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