Combating the Buzzkill

If you woke up tomorrow morning to find out that okra had disappeared from the face of the earth forever, would you miss it? Probably not, no.

What about a future devoid of apples and watermelons, or almonds and coconuts? Would you mourn the loss of lemons, figs, blackberries, and pears? What of cocoa, vanilla, and walnuts?

What about your morning coffee?

Each of these beloved foods we owe to the work of honey bees, who shoulder the burden of pollinating an estimated $40 billion worth of America’s agricultural produce every year. On a global scale, these little animals facilitate the production of one-third of the entire planet’s crops.

Yet it is no secret that honey bees have experienced massive die-offs at unprecedented rates, with numbers of hives decreasing by the tens of millions. On average in the last 10 years, beekeepers across the nation have reported losing around 30 percent of their colonies each winter, with some overall annual losses spiking as high as 42 percent.

The driving forces behind the now rampant phenomenon of Colony Collapse Disorder (CCD), where entire colonies of worker bees mysteriously abandon their queen and hive, continue to perplex researchers. In fact, part of the difficulty of combating the stressors responsible for honey bee deaths is identifying those stressors in the first place. This is not a classic whodunnit scenario in which the clues inevitably concede that Mr. Monsanto committed the crime in the cornfield with a candlestick–or a neonicotinoid pesticide, in this case.

The reality is far more complex. On this game board, every player is a culprit: pesticides, pathogens, viruses, fungi, parasites, poor colony management, deforestation and subsequent habitat destruction, food scarcity, drought, and global warming. To further complicate matters, these stressors often function synergistically, making it difficult for researchers to predict the outcomes of their interactions.

Of these many issues that exert negative impacts on honey bees, perhaps the greatest scourge to global population is one of the smallest: a parasitic mite known around town by its scientific super-villain name, Varroa destructor.

Varroa feed on hemolymph, an invertebrate’s circulatory equivalent of blood, by attaching themselves to larval and adult honey bee hosts. The vampiric, pinhead-sized mites may look tiny to us, but relative to a honey bee’s body, they make for pretty hefty passengers. Imagine going about your day with three to four lobster-sized ticks stuck to your torso. (Now wipe that image from your mind and accept my sincerest apologies for putting it there.)

A Varroa destructor. Photo courtesy of Gilles San Martin.

In addition to suppressing bees’ immune systems, the mites act as extremely effective vessels for carrying and transmitting disease. If gone untreated, the presence of V. destructor delivers an incontrovertible death kiss to western honey bee colonies, which can die within one year of the pest’s appearance. Even worse, the miticides used to treat Varroa have been found to produce adverse health defects in the honey bees they were engineered to protect, while predictably, the mites have developed an immunity to the pesticides.

The honey bees that pollinate so much of our homeland are not actually endemic to America. These fuzzy creatures arrived here on the hems of early European settlers, and are therefore still called European honey bees. All over the globe, honey bees provide the same vital services to agricultural systems.

“People say the greatest animal in Africa is the lion or the elephant,” said Harland Patch, a research scientist at Penn State’s Department of Entomology. “But honey bees are more essential, and their decline would have profound impacts across the continent.”

In 2010, Patch was part of a team of researchers that received a grant from the US National Science Foundation to embark on the largest survey of African honey bees ever undertaken. The group, which consisted of researchers from Penn State, South Eastern Kenya University, and the International Centre of Insect Physiology and Ecology (ICIPE), visited 24 sites in Kenya in order to monitor the presence of viruses and pests in colonies.

It was only one year prior that they had discovered the presence of Varroa mites in Kenya for the very first time. This second visit revealed that the mites had since spread throughout Kenya and into Tanzania, sparing only the remote colonies of the far northeastern deserts near Somalia.

Unlike the European honey bee, however, the African honey bees infested with mites seemed to be doing just fine. And where colonies possessed no mites, they exhibited no viruses, confirming the researchers’ belief that Varroa play a substantial role in the distribution of maladies throughout colonies.

“It was really interesting to us that the bees there did not appear to be collapsing under the weight of mites and the viruses that come along with them,” Maryann Frazier, senior extension associate in the Department of Entomology at Penn State, tells BTR.

Frazier explains that certain African bee-specific behaviors, such as a particularly strong knack for locating and disposing of diseased brood, may be responsible for the bees’ apparent resistance to mites that decimate similar populations elsewhere.

As far as effectively sequencing genomes from the Kenyan bees in search of specific genes that may underlie their tolerance to mites, researchers are still a ways off. In the meantime, Frazier believes our greatest hope lies in the development of captive-bred “survival” stock.

“What we’re really interested in are the mechanisms that allow [the African honey bees] to be more resistant,” she said. “And then we can use that knowledge to select for those behaviors and physiological traits.”