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Why It's So Hard to Figure Out What's Killing the Bees

Researchers have been testing a number of theories, but the answer seems to lie in a confluence of interacting factors.
May 15, 2015, 11:00am

We first realized the bees were all disappearing back in 2006, yet despite years of government-funded research, they're still dropping off in droves.

Earlier this week the Department of Agriculture released its annual survey of managed bee colonies (those are bees that are kept by people for pollination or honey, as opposed to wild bees). According to the survey, 42.1 percent of managed colonies died between April 2014 and April 2015. In the same period the year before, 34.2 percent of colonies were lost. The bees are still disappearing, and the problem is getting worse.


A big factor is the mysterious Colony Collapse Disorder (CCD), a still largely-unexplained phenomenon where entire colonies of managed bees vanish from the hive without explanation, often leaving behind a live queen and fresh honey. But even as signs of CCD are declining, the bee numbers are continuing to drop at an alarming rate, and experts who study the insects are still juggling a wide range of theories for what's contributing to the losses.

"The winter loss numbers are more hopeful especially combined with the fact that we have not seen much sign of Colony Collapse Disorder (CCD) for several years, but such high colony losses in the summer and year-round remain very troubling," Jeff Pettis, a survey co-author, said in a press release. "If beekeepers are going to meet the growing demand for pollination services, researchers need to find better answers to the host of stresses that lead to both winter and summer colony losses."

And they're trying, because when it comes to our food production, bees (both wild and managed) are even more important than fertilizer. The USDA estimates every third bite of food we eat benefits from honey bee pollination. If the bee numbers continue to drop at this rate, the cost of food could soar. We need these little guys.

In Beltsville, Maryland, a team of entomologists, biologists, and physiologists (including Pettis) make up the USDA's bee research laboratory. The lab is a project of the department's agricultural research service that has been hunting for clues about what's killing our bees since CCD first emerged nearly a decade ago.


The bee lab is attacking the problem with a wide breadth of research. They're investigating what effect low, sustained doses of pesticides has on bees: too low to kill the bees in one fell swoop, but perhaps we're slowly poisoning our pollinators. They're sequencing the genome of healthy bees and bees that have suffered CCD to look for differences. They're studying parasites like the Varroa mite and viruses like Israeli Acute Paralysis Virus (IAPV) that have been closely linked to CCD to see what role these other ailments play.

Judy Chen, an entomologist at the ARS bee lab, led research into IAPV for seven years and discovered how severe the virus was: it could be transmitted through pollen and nectar and was even discovered in bees' reproductive systems.

"It was in the queen's reproductive organ. The infection in those tissues suggests this virus could also be transmitted locally, flowing from the infected mother queen to the offspring," Chen told me over the phone.

While she found the virus had a significant impact on bee colonies and was closely linked to CCD, she was unable to establish a cause-and-effect relationship between the two.

The years of research (there are lots of bee labs at universities across the US that work with the USDA, too) have yielded some best practices that Chen said can help reduce the risk of CCD: the bee lab recommends creating a diverse foraging habitat for bees and limiting pesticide use during foraging season. It's also created a valuable resource for beekeepers, who can send sick bee samples to the lab for diagnosis and track research online while also providing up-to-date data on their colonies.

But Chen said the biggest challenge is the fact that, more and more, they're discovering the massive bee die offs are not the result of one single factor. There's no one pesticide or virus or parasite that's causing our bees to vanish, but a number of influences working together. A pesticide can make a bee more susceptible to a virus, which it can catch from a parasite that has invaded the hive.

"There are dozens of factors working together," Chen said.