Trying to Diagnose the Disappearing Bees

Trying to Diagnose the Disappearing Bees

UCSD graduate student Daren Eiri tries to attract bees into a 26-foot-long tunnel used to train the insects to find a reliable food source. Photo: Sam Hodgson

Sunday, Nov. 8, 2009 | Witness the yellow- and black-striped swarm buzzing around Daren Eiri as he works, and you wouldn’t think honeybees are in short supply. Dozens of fuzzy, winged insects blanket a grapefruit-sized glass dish in Eiri’s hand one warm afternoon at UCSD’s Biology Field Station.

“I used to hate doing this,” said Eiri, a University of California, San Diego graduate student, who at the moment is a perch for honeybees occasionally landing to lick sugar from his skin. “When they’re feeding I’m pretty sure they’re only concerned with food.” Eiri puts a squat cup of sweet liquid on top of the plate and sets the feeder inside a wooden tunnel.

But this bee-rich environment is deceptive: Eiri and the James Nieh Bee Lab at UCSD are researching a serious but poorly understood phenomenon known as Colony Collapse Disorder. Despite the bees flying like popcorn up and down Eiri’s carefully constructed passageway, these pollinators are perishing at an unprecedented rate in the United States and the world.

“[Bees] have a finely tuned and actually amazing navigation system,” said Nieh, an associate biology professor at UCSD. “When you think about the size of a bee compared to a size of a human, it would be like you were to walk or run somewhere for hundreds of miles and yet be able to go back precisely to your house without any trouble at all.”

However, this navigation system appears to have gone haywire in an alarming number of European honeybees. They simply aren’t returning to their nests, often leaving the queen, a few infants and a seemingly normal comb of honey. Since 2006, nearly a third of all hives worldwide have come up empty.

If the trend continues, we won’t have enough bees to pollinate many of our most popular fruits, vegetables and nuts, researchers say. Some 85 commercial crops — things like avocados and asparagus, peanuts and peaches — depend on honeybee pollination.

The Nieh Bee Lab at UCSD is among the top research groups investigating possible causes of Colony Collapse Disorder. The key suspects so far are viruses, parasitic mites, poor nutrition, excessive travel and pesticides.

The lab is honing in on a chemical called Imidacloprid, one of the most common pesticides for produce like lettuce and strawberries. In 2007, farmers sprayed almost 340,000 pounds of the chemical on California crops — twice as much as the year before.

Imidacloprid was banned in some European countries for harming honeybees, and is now under review by state and federal environmental regulators in the United States.

The UCSD lab is examining a new angle to the problem — specifically how Imidacloprid affects bees’ ability to navigate and ultimately find their way home. Nieh’s team is feeding bees Imidacloprid in doses comparable to what they’re ingesting in the field, then flying them through a marked tunnel to track their reaction.

Bees in Training

On a recent afternoon, Eiri — who was once terrified of getting stung but has grown bold enough to ditch his bee suit — attracts honeybees with a sugar and water mixture he’s positioned in the 26-foot-long tunnel. Bees smell the sweet fragrance and fly into either side of the open-ended structure to feed.

What is lunch for the bees is actually a training exercise.  The honeybees learn where to find a reliable food source, just as they do with blossoms in the wild.

With bare hands, Eiri reaches under a wire screen on top of the tunnel and paints yellow dots on the thorax of 20 bees. He uses a pipette to hand feed them a pesticide-laced tincture.

The next day Eiri releases the labeled bees, along with a control group, into a tunnel seemingly identical to the first one, except it’s void of food. Bees use optical cues in their environment to calculate how far they’ve traveled — in this case, black and white stripes lining the passageway’s interior. Eiri documents how the two groups of bees navigate the barren tunnel on a quest for the sugary drink.

Early results show pesticide-fed bees act differently than their untouched counterparts. They’re making critical errors, becoming disoriented and flying farther than they should in search of food.

“Bees that are fed pesticides are searching a much wider distance than normally treated bees,” Eiri said. “Because they’re using much more energy to find food they might not have enough energy to come back to the colony, which would lead to collapsed colonies.” If the worker bees don’t make it back to the nest, young bees waiting for nectar will starve.

Eiri’s experiment is timely. The U.S. Environmental Protection Agency is getting an outpouring of complaints that Imidacloprid harms pollinators — 12,000 objections last year alone. The EPA is gathering new data from manufacturers and scientists, like the Nieh Bee Lab, to reconsider the chemical’s safety. The earliest it will make a decision on the pesticide, however, is 2014.

The chemical is also being reviewed by the California Department of Pesticide Regulation based on new evidence that residue levels actually increase over time. The current label warns users to spray only when bees aren’t present, but recent data suggests leftover residue could kill bees long after the chemical has been sprayed.

“We have known since it was registered in the mid-1990s Imidacloprid was highly toxic if bees were exposed during treatment of the pesticide or residues were remaining on blooming crops or weeds,” said Rick Keigwin, the U.S. EPA’s director of pesticide re-evaluation.

Scientists say newer studies suggest Imidacloprid can also impair learning, memory and immune function in honeybees.

“We need to not only look at whether the bees are belly up,” said Tim Lawrence, a research associate at Washington State University. “We need to look at: ‘Is it impacting their ability to be efficient pollinators?’ That’s the important role they play.”

No Easy Answers

Other bee experts caution against making Imidacloprid the lone culprit. Eric Mussen, an apiculturist with the UC Cooperative Extension, agrees that pesticides may knock down bees’ immune function. But he counters that a ban in France and Germany didn’t bring a resurgence of honeybees.

“There are people convinced that particular pesticide is the reason for colony collapse disorder,” Mussen said. “I’m almost as convinced if you just took that pesticide away things would not suddenly get better. It didn’t in Europe.”

Jim Oakley, who has kept bees for four decades, defends insecticides as safe and vital for our food supply. The Ramona beekeeper has lost 600 of his 2,000 colonies this year alone. But Oakley chocks that up to the rigors of modern-day bee life and an artificial diet of corn syrup and imitation pollen — not pesticides.

“Without insecticides most of our crops wouldn’t be there either,” Oakley said. “They can be wiped out overnight with bugs.”

Also, Oakley said, hives that aren’t directly exposed to pesticides collapse equally as often as those that pollinate avocados where fungicides are common.

But Jim Frazer, an insect physiologist at Pennsylvania State University, said with the lingering residue, we don’t know which bees are ingesting Imidacloprid or when. Frazer adds this is not just about one pesticide; there’s no scientific literature on the interaction of multiple chemicals sprayed on today’s crops.

“Sometimes we’ve found as many as 33 pesticide samples in a given pollen sample,” Frazer said of his research. “It’s pretty alarming.”

Researchers say the stew of pesticides could further pre-dispose bees to the deadly varroa destructor mite, a blood-sucking pest that has ravaged honeybee hives for the past 20 years.

The transient lifestyle of honeybees servicing agribusiness also gives mites an edge, said entomologist W. Steve Sheppard of Washington State University. Sheppard said bees that would naturally hunker down for a cold winter are trucked to temperate climates where mites thrive. Bees from around the country, for instance, are being shipped to California almond groves, which require more pollination than any other crop.

“There is additional stress brought about by this system,” Sheppard said. “The fact that you load them on a truck and drive them a thousand miles, unload them and expect them to work for three weeks and load them on a truck and move them somewhere else.”

Commercial agriculture is in jeopardy if the bee problem goes unabated, said Meg Eckles, a doctoral student in UCSD’s Nieh Bee Lab. Pollinated crops are valued at $15 billion in the United States alone.

“So much of our economy is based on products that honeybees pollinate for very little money,” Eckles said. “They’re very inexpensive pollinators. If they were to disappear, it would have huge economic consequences that could be very devastating to the U.S.”

Despite the nine stings he’s suffered, Eiri has developed a deep appreciation for honeybees and hopes his research will ultimately help regulators safeguard the pollinators.

“We don’t know the issue exactly of what’s causing Colony Collapse Disorder,” said Eiri. “But it’s frightening to know that if this can’t be resolved the bees will disappear in the future.”

Rebecca Tolin is a San Diego-based freelance writer. Please contact her directly at rebeccatolin@yahoo.com with your thoughts, ideas, personal stories or tips. Or set the tone of the debate with a letter to the editor.

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