The Secret Death of Bees

by Eric Sorensen | © Washington State University

It’s not easy being a honey bee.

A mite with the last name of “destructor” routinely sucks its blood. A fungus augers into its gut, compromising its immune system and robbing it of nutrients. There’s a lot of time on the road—a California almond grove one week, a Washington apple farm the next—and the diet can be monotonous and not the most nutritious.

Then there are the living conditions. Recent work at Washington State University found hives tainted by more than five dozen different pesticides.

It’s all a bit much, say WSU researchers giving special attention to the mysterious Colony Collapse Disorder that has been hammering hives in recent years. While the disorder is having the impact of a flu epidemic, the WSU work strongly suggests it stems from several causes that, in concert, are making the tough life of a bee that much tougher.

“There are so many stresses on the bee, being raised in brood combs with high levels of pesticide residues adds just one more thing,” says Steve Sheppard, a WSU entomologist.

He quickly adds that the disorder is hard on the beekeepers, too. In each of the last three years, beekeepers across the country have lost one-fourth to one-third of their colonies, according to the Apiary Inspectors of America and the U.S. Department of Agriculture. Many of these losses are being blamed on Colony Collapse Disorder.

Jerry Tate, president of the Washington State Beekeepers Association and a Spokane honey producer, says some hobby beekeepers have had 50 to 80 percent losses. Several commercial operations, which help pollinate many of the state’s top crops, have lost as much as 50 percent a year.

Yakima’s Eric Olson, one of the largest beekeepers in the Northwest, has been hit repeatedly. He suspected more trouble was on its way last August when his western Washington hives, one of three sets he keeps in various locations, started to struggle. He supplemented the bees’ diet with syrup and pollen, and they eagerly processed what he gave them. Then, on November 1, he found their hives completely empty, an apian version of colonial Roanoke Island.

“They simply disappeared,” Olson says.

Desperate for a solution, beekeepers, growers, Governor Chris Gregoire, WSU’s Agricultural Research Center and the Washington State Department of Agriculture provided funds in 2008 to establish a Honey Bee Colony Health Diagnostic Laboratory at WSU.

The laboratory now has five people working on colony health. They include Matthew Smart and Judy Wu, two master’s students who came to WSU knowing basically nothing about bees. Now they approach being a modest power couple of Northwest bee research.

“These kids are superstars,” says Olson. “The entire industry is captivated by the work they’re doing.”

In a meeting last fall of the California State Beekeepers Association, beekeepers ranked and funded 13 different research proposals. Smart and Wu’s proposals were ranked second and third.

Smart has focused on Nosema ceranae, a relatively new and little known fungus. With repeated sampling and DNA analysis, he determined that the fungus has become more common than its more widely known cousin, Nosema apis. Smart says the fungus has been shown to suppress a bee’s immune system, draining its energy and reducing the number of bees returning to the hive.

“It’s possible that a lot of these bees are dying because they’re just not able to get enough nutrients in their diet,” Smart says.

But it’s not a smoking gun.

“Instead of looking for one single factor causing colonies to collapse, it’s more important now to be looking at interactions of these factors,” Smart says. His thinking is underscored by research in the peer-reviewed online journal PLoS ONE suggesting the colony collapse involves as many as 61 possible variables.

Among them are pesticide levels. Wu tested brood combs, the breeding quarters of the hive, and found they contained 66 different pesticides. Most were insecticides, more than three-fourths of which are toxic to bees. But the less-than-toxic pesticides concern her as well.

Regulators focus on how much chemical it takes to kill a bee and test one chemical at a time, says Wu. But they do not look at the combined effects of chemicals, which can be 10, 100, even close to 1,000 times more toxic. The chemicals also affect a bee’s nervous system, behavior and larval development.

The impact can ripple through a colony. A tainted forager can contaminate the hive with pesticides, which can reduce the number of eggs laid by the queen and impair workers’ memory and spatial orientation. If a poisoned adult dies, younger bees can be forced to serve as foragers, leaving fewer bees to tend to the brood, perform household tasks and process food for the winter.

In one test, Wu found that a contaminated hive delayed larval development, giving the blood-sucking mite Varroa destructor more time to produce offspring in the hive.

“We’re continuing to run out of safe chemical control measures for this mite, which has a very rapid life cycle. Due to the high rate of reproduction, mites can quickly develop resistance to pesticides,” says Sheppard. “The long term answer will come through genetic improvement of the bees. And in the meantime, beekeepers need to use whatever control measures they’re using as judiciously as possible.”

For now, the lab is recommending that beekeepers change their combs more regularly to reduce the pesticide load. It’s not a perfect solution, costing beekeepers money and bees a fair amount of energy. Ultimately, the researchers hope to guide solutions that will make things easier on the bees and tougher on the pests that plague them.

Colony collapse disorder (CCD), or sometimes honey bee depopulation syndrome (HBDS), 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, the term colony collapse disorder was first applied to a drastic rise in the number of disappearances of Western honey bee colonies in North America in late 2006. Colony collapse is economically significant because many agricultural crops worldwide are pollinated by bees.

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%. Possible cases of CCD have also been reported in Taiwan since April 2007.

The cause or causes of the syndrome are not yet fully understood, although many authorities attribute the problem to biotic factors such as Varroa mites and insect diseases (i.e., pathogens including Nosema apis and Israel acute paralysis virus). Other proposed causes include environmental change-related stresses, malnutrition and pesticides (e.g.. neonicotinoids such as imidacloprid), and migratory beekeeping. More speculative possibilities have included both cell phone radiation (e.g.) and genetically modified (GM) crops with pest control characteristics, though no evidence exists for either assertion. It has also been suggested that it may be due to a combination of many factors and that no single factor is the cause.

Applying proteomics-based pathogen screening tools in 2010, researchers announced they had identified a co-infection of invertebrate iridescent virus type 6 (IIV-6) and Nosema ceranae in all CCD colonies sampled. These results, if confirmed, may finally offer an explanation for genuine cases of CCD. On the basis of this research, The New York Times reported the colony collapse mystery solved, quoting researcher Dr. Bromenshenk, a co-author of the study, “[The virus and fungus] are both present in all these collapsed colonies.”

European honey bee populations have recently faced threats to their survival. North American and European populations were severely depleted by varroa mite infestations in the early 1990s, and US beekeepers were further affected by Colony Collapse Disorder in 2006 and 2007. Chemical treatments against Varroa mites saved most …

The honey bee’s primary commercial value is as a pollinator of crops. Orchards and fields have grown larger; at the same time wild pollinators have dwindled. In several areas of the world the pollination shortage is compensated by migratory beekeeping, with beekeepers supplying the hives during the crop bloom and moving them after bloom is …

The honey bee is a colonial insect that is often maintained, fed, and transported by beekeepers. Honey bees do not survive individually, but rather as part of the colony. Reproduction is also accomplished at the colony level. Colonies are often referred to as superorganisms.

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Periodically, the colony determines that a new queen is needed. There are three general triggers.

1. The colony becomes space-constrained because the hive is filled with honey, leaving little room for new eggs. This will trigger a swarm where the old queen will take about half the worker bees to found a new colony, leaving the new queen with the other half of worker bees to continue the old colony.
2. The old queen begins to fail. This is thought to be recognized by a decrease in queen pheromones throughout the hive. This situation is called supersedure. At the end of the supersedure, the old queen is generally killed.
3. The old queen dies suddenly. This is an emergency supersedure. The worker bees will find several eggs or larvae in the right age-range and attempt to develop them into queens. Emergency supersedure can generally be recognized because the queen cell is built out from a regular cell of the comb rather than hanging from the bottom of a frame.

Regardless of the trigger, the workers develop the larvae into queens by continuing to feed them royal jelly. This triggers an extended development as a pupa.

When the virgin queen emerges, she is commonly thought to seek out other queen cells and sting the infant queens within and that should two queens emerge simultaneously, they will fight to the death. Recent studies, however, have indicated that colonies of Apis mellifera may maintain two queens in as many as 10% of hives. The mechanism by which this occurs is not yet known, but it has been reported to occur more frequently in some South African subspecies of Apis mellifera. Regardless, the queen asserts her control over the worker bees through the release of a complex suite of pheromones called queen scent.

After several days of orientation within and around the hive, the young queen flies to a drone congregation point – a site near a clearing and generally about 30 feet (9.1 m) above the ground where the drones from different hives tend to congregate in a swirling aerial mass. Drones detect the presence of a queen in their congregation area by her smell, and then find her by sight and mate with her in midair (drones can be induced to mate with “dummy” queens if they have the queen pheromone applied). A queen will mate multiple times and may leave to mate several days in a row, weather permitting, until her spermatheca is full.

The queen lays all the eggs in a healthy colony. The number and pace of egg-laying is controlled by weather and availability of resources and by the characteristics of the specific race of honeybee. Honey bee queens generally begin to slow egg-laying in the early-fall and may even stop during the winter. Egg-laying will generally resume in late winter as soon as the days begin to get longer. Egg-laying generally peaks in the spring. At the height of the season, she may lay over 2500 eggs per day – more than her own body mass.

The queen fertilizes each egg as it is being laid using stored sperm from the spermatheca. The queen will occasionally not fertilize an egg. These eggs, having only half as many genes as the queen or the workers, develop into drones.