Understanding Colony Loss
This year overwinter losses of honey bee colonies have reached an all-time high in North America, and honey bee health continues to be a top priority for the agriculture industry. Debate over possible causes of declining bee health continues in many nations throughout the world, but many experts say there is no one simple answer to this issue.
This five-part series will examine the health and welfare of the honey bee, whose future may have a substantial effect on critical industry decisions.
Roughly one-third of the food we consume is reliant on the tireless labor of pollinators. And Apis mellifera, the honey bee, is the only pollinator capable of being managed on a scale large enough to satisfy the demands of the global agriculture industry, making honey bees indispensable partners in the pursuit of feeding the masses.
“Almost all of the dietary items that we like to eat and that are good for us are highly dependent on the honey bee for pollination,” says Iain Kelly, bee health issues manager with Bayer CropScience. According to Bayer, there are approximately 25,000 to 35,000 commercial beekeepers in the United States, and honey bee pollination services are estimated to provide $40-billion worth of added value to crops worldwide every year.
Introduced to North America from Europe in the early 17th century, honey bees require large quantities of nectar and pollen to rear their young and produce honey. In commercial use, honey bees are treated as managed livestock. The hives support high populations of bees, and are transported by beekeepers to farmers’ fields to provide mass pollination of crops.
The commercial pollination industry has been experiencing losses of adult worker bees since the mid-’80s. Across the globe, bees have been dying off at alarming rates—in some cases whole colonies at a time.
“Most of the general public has no clear idea of how we produce food in this country, or the challenges faced by the agriculture industry,” says George Hansen, president of the American Beekeeping Federation. “Honey bees are threatened. Generally, the bees cannot survive without intervention from humans to protect them from pests, and to supplement their nutrition.”
Continuing decline of bee health and populations will have economic and ecological repercussions. Experts warn without the intervention of industry stakeholders, continued large annual losses of bee colonies will cause financial stress on the beekeeping industry, which could become unprofitable and, in turn, trigger greater risks to global food security. “It is an economic hardship for [beekeepers]; it costs more in labor, buying queens and modification to management procedures, so they will not be in a financial position to make the increases they need to maintain a profitable business,” says Dick Rogers, an apiologist with Bayer’s Bee Care Center. Without honey bee pollination services the agriculture industry will be forced to invest in alternative solutions for pollination or create financial incentives for honey bee beekeepers.
Some beekeepers who have faced these dramatic losses found their once healthy hives mostly empty, with only the queen bee and a few worker bees remaining. Foraging bees had apparently left the hive and never returned. This disappearance of foraging bees ultimately leads to the demise of entire colonies, leaving hives with excess brood and very few bee remains. In the mid-2000s, these symptoms were labeled colony collapse disorder; however, there are many disorders that negatively affect bee health, and these can result in a variety of symptoms.
According to a number of apiologists, multiple stressors have created the perfect storm of vulnerability, where the declining health of bees makes them more susceptible to viruses and disease pathogens.
The reason for the die-offs puzzled beekeepers and researchers alike. Since the late 1990s, there have been many scientific studies into possible causes of colony deaths. Through this research, some experts are now refuting the validity of CCD, calling it a convenient, simplistic label for what is actually a very complex problem.
“CCD is a term that causes a lot of confusion. There is this belief that the bees are disappearing. It is not that they are disappearing—it is that the hive is dying from multiple factors,” says Kelly. “When we begin to look at … why these bees are dying off, the public doesn’t understand, to a certain extent, what is done with the honey bee, how it is moved, the kind of needs that have to be met in order to survive … because of that, they begin to point at simplistic solutions as ways to improve honey bee health.”
According to a number of apiologists, multiple stressors have created the perfect storm of vulnerability, where the declining health of bees makes them more susceptible to viruses and disease pathogens. Scientists have identified more than a dozen different factors that contribute to the overall decline in honey bee health, including habitat and forage loss causing nutrition deficiency, introduced parasites, varroacide use, emerging new viruses, other bee disorders, hive management and possible exposure to pesticides.
“They label these die-offs as CCD, but it’s not really a disorder because that would suggest it is caused by one factor. It is more of a syndrome or an undescribed cause,” explains Rogers. “We like to think of it as a general decline of bee health and that they are reacting in different ways to the different combination of stressors affecting them.”
Throughout history there has always been overwinter loss of honey bees. Before the mid-’80s, beekeepers typically lost five to 15 percent of their colonies annually. “The main culprits at that time were starvation, old queens and simpler problems,” says Rogers.
Beekeepers consider the varroa mite their greatest obstacle in maintaining healthy colonies.
Photos courtesy of Bayer CropScience.
“Since the mid-’80s, shortly after the introduction of the varroa mite, we have had very high losses. Then controlled management of the mites pulled those loss numbers back again. A few years later the mites became resistant to those treatments and the losses have been going up ever since.”
Beekeepers consider the varroa mite their greatest obstacle in maintaining healthy colonies. Known as the vampire of the bee world, varroa mites feed on bee blood and reproduce on bee brood, spreading viral diseases such as deformed wing virus and chronic paralysis. Mites are vectored by bees which can then spread them from hive to hive. “If a beekeeper does not have a successful mite control program, their hives will die—period,” says Hansen. “There is no refuge, no style of hive or breed of bees that will change that fact.”
Average overwinter losses recorded since the introduction of the varroa mite have been in the range of 30 to 35 percent. Some experts have predicted that without corrective action to control mites and other bee disorders, overwinter losses could reach 50 to 60 percent this spring. “This is one of those years when it was clear that mites were getting out of control,” says Rogers. “There were other factors involved as well, but that 50 to 60 percent loss has become a reality this year because those disorders weren’t managed properly.”
Overwinter colony losses have hit an all-time high in North America, but to many industry stakeholders, this comes as no surprise. “Last year was a good year. And so a lot of beekeepers and researchers were predicting, because of the cyclical nature, this year would be a bad year, especially if people didn’t get the varroa mite under control quickly,” says Kelly.
At the start of last year, honey bee populations were the strongest they had been in years, with only a 22 percent overwinter loss going into the 2012 growing season. However, this also created the perfect opportunity for the varroa mite and other pathogens to flourish. “Because last year was a mild winter and the bees came out strong in the spring [in 2012], the mite came out strong in the spring as well,” says Kelly.
“If the colony has a big honey crop, and raises lots of bees to make the winter cluster large and healthy, then they have a good start the next year. … 2012 was the smallest domestic honey crop every recorded.”
In the fall, in order for a colony to survive the winter and emerge in the spring with strong numbers, it is essential for the colony to build up a large honey supply, helping to create strong winter bees that are free of disease and parasites. “If the colony has a big honey crop, and raises lots of bees to make the winter cluster large and healthy, then they have a good start the next year. Conversely, a poor crop, with poor conditions going into the winter, will generally cause weak winter clusters, higher mortality and small hives starting the next season,” explains Hansen. “2012 was the smallest domestic honey crop ever recorded.”
Beekeepers are now entering the recovery phase, building up colony populations for this year’s pollination season. This is a naturally occurring process in nature, but commercial beekeepers speed up this process by splitting colonies; a second queen bee is produced, colonies swarm and then begin the task of reproducing to build up their numbers. Some experts believe that through proper hive management it’s possible to regain sufficient honey bee numbers before the coming winter months.
“I think what is going to happen is this is going to follow a host-parasite relationship where the parasite, and attempts to manage the parasite, has resulted in a huge loss of the host, the honey bee. Now we are going to replace and replenish the host in a healthier environment, so I expect whatever numbers we get back to this year will survive very nicely over the winter. I foresee we will have a very low winter loss next season,” says Rogers.
Many organizations in the United States and around the globe are pursuing initiatives to determine the most effective ways to mitigate colony losses and return honey bee populations to a more stable state. With many die-offs having already occurred this spring, agriculture professionals are being urged by experts to seek out information on the various issues affecting honey bee health. “It would be beneficial for people to work with beekeepers, talk to beekeepers, and understand what they are truly facing,” says Kelly.
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