More Science Talk
May Berenbaum, entomologist at the University of Illinois at Urbana–Champaign and inspiration for the X Files fictional entomologist Bambi Berenbaum, talks about colony collapse disorder and disappearing bees, as well as the importance of honeybees in agriculture.
Steve: Welcome to Science Talk, the weekly podcast of Scientific American posted on August 14th, 2009. I'm Steve Mirsky. This week we'll hear about bees and what's ailing them with renowned entomologist May Berenbaum; she's on the faculty at the University of Illinois at Urbana–Champaign and has written many popular books including Bugs in the System, The Earwig's Tail and Ninety-Nine Gnats, Nits and Nibblers. She and her student Reed Johnson have also been trying to figure out what's behind the mysterious disappearance of honeybees, known as colony collapse disorder. In part 1 of the podcast, you'll hear the talk that Berenbaum gave to a group of students at the annual meeting of the American Association for the Advancement of Science, back in February. Now May did not know going in that the students were going to be little kids, so on the fly, she revised her talk to be more understandable to the grade-school students which worked great for me and I hope it will for you, too. Next time in part 2, I am going to play an interview I did with Berenbaum after her talk and I will also share a conversation I had in England in early July with an uncommonly charming gentleman with the common name of John Williams. He is the bee keeper at Down House, Darwin's home. Well, right now, without any further ado here's May Berenbaum.
Berenbaum: The organizer[s] asked if I would talk about an entomological mystery and how entomologists and other scientists go around solving mysteries; and specifically this mysterious disappearance of the bees: Where have all the bees gone and why do we need to find them? Well I guess, first part of the mystery is which bees are missing. A lot of people when they say "bee" don't realize there is over 4,000 different species of bees in North America. So the first thing to establish is which one is missing. If any, in fact the bee that every one is concerned about is called the Western honeybee; it's known Apis mellifera, that's the scientific name. The word Apis is Latin for "bee" and mellifera means "to carry honey", and that's way everybody calls this the honeybee. Although technically it does not quite carry honey, it carries nectar from flowers which it brings back to the hive and makes into honey. So the bee that everyone is worried about is called the Western honeybee; that's Apis mellifera. So even though it is called the honeybee, everybody knows what honey is, it's sweet, it's a treat on your toast [or] your tea, and it's worth a lot of money. It's worth about $150 million in the U.S. economy. But what people don't realize is honeybees are far more economically important not for making honey or making wax or making supplements for health food bars but for a service they provide. They provide the service that's called pollination. You've all heard about the birds and the bees, well it literally it does involve the bees; pollination is basically plant sex. Plants are rooted to [the] ground and when it comes time to find a mate, they cannot get up and move and go to a singles bar, they have to rely on some mobile partner to help them. And in fact for about three-quarters of the flowering plants on this planet, they rely on insects to help them [on] an animal partner. So basically that's what pollination is. Pollen grains are male sex cells. They have to get to the female parts of the flower. Plants can't walk around and deliver them themselves, so often it's a winged partner, like a bird or a bat or a bee that brings the male sex cells in contact with female sex cells.
Honeybees are very important in agriculture. They help plants reproduce, so about 200,000 species of plants rely on insects and a majority of those rely on bees. Well, we rely on bees, as well, because we grow crops to eat them, and in order to produce fruits and vegetables, and nuts and the like, those flowers have to be pollinated. We can't do it. So we have recruited a partner, the honeybee, as our pollinator partner. There are lots and lots, well there's 4,000 species of bees. Why do we settle on this [one] species of bee to be our partner? Well, the honeybee is called a social insect. That doesn't mean it goes to parties; it means it lives in family groups with about 30–50,000 individuals. So 30[,000] to 50,000 agricultural workers if you will, in one colony. Another really useful attribute to the bee is that the honeybee can communicate to its nest mates. It has a symbolic language called the dance language and it can tell its nest mate where particular types of flowers are, like bee GPS. They can actually figure out where they are and tell directions to their nest mates. So if you have a whole field full of watermelons and you want the bees to pollinate the watermelons, the first bee will come back and tell the other bees where the watermelon patch is. They also, unlike some species of bees, feed on just about anything. They are not fussy; they will pollinate hundreds of different species of flowers. There are some bees like, you might guess, the native squash bee, it's called the squash bee because that's the only plant it pollinates, the squash. Honeybees will pollinate almost anything you can think of, almost all [our] fruits, almost all of our vegetables and most of our nuts are pollinated by the honeybee.
So, pollination service[s] in agriculture are worth about $15 billion, this one insect. I think the best way to illustrate how influential the honeybee's contribution to U.S. food production is [is] to talk about a Big Mac. Everybody knows what a Big Mac is, right? Well, without a honeybee, there'll be no all[-beef] paddies. Why? Cows are not pollinated? Well, we feed cows clover and alfalfa hay. And in order to grow clover and alfalfa—Guess what? You need bees to pollinate those flowers. No cheese right? Because cheese comes from dairy cows which eat alfalfa and clover. So a Big Mac has no all [beef] paddies, no lettuce, no onions, no pickles, no cheese—you'd have the bun because wheat is a wind-pollinated plant, doesn't need insects, no sesame seeds; and I don't know what's in special sauce, but I'll bet it requires bees.
So beekeepers then are actually, they deliver, they put wheels on our bees. So bees can fly between flowers, but it's very hard for the bees to go from one crop to another. Beekeepers today, called migratory beekeepers, load those bees in boxes onto the backs of trucks and drive them thousands of miles across the U.S. to pollinate citrus in Florida, blueberries in the Northeast, clover in the Northwest and almonds in California. In fact, if there's anybody who likes almonds, you have a bee to thank; you cannot produce almonds without honeybees. Every February, half of America's honeybees, 1.25 million honeybees, travel to California, just to pollinate almonds. So if you had an Almond Joy bar or Almond Snickers or almond M&Ms you have a bee to thank for that; and a beekeeper who delivers the bees.
Okay, so what's all the fuss, what's all the concern? Well in November of 2006, little over two years ago, a very big beekeeper, who had thousands of colonies, discovered that his bees were not dying, just disappearing. He put them in for the winter in Florida and he went to check on them, and they were gone. Normally there are 30–50,000 workers, there's a bunch of grubs or babies and lots of stored food, and he went and checked them and the workers were gone. there were no dead bodies, they just disappeared. He started talking to his colleagues and a lot of beekeepers reported missing bees; and this was a major shock to the industry. Nobody knew where the bees went; nobody knew where the bodies were. The concern was, maybe this is a new disease. The bees were maybe dying away from the hive, and they were leaving their queen behind and all their babies behind. And what was really alarming to people, you think about one hive can produce a hundred pounds of honey—that's an irresistible temptation to all kinds of hive pests, but even hive pests were leaving these colonies alone. Now bees have periodically disappeared, since about the 1880s, every now and then bees mysteriously disappear. The disappearances in the past were very localized and very short term. So this particular disappearance, which we came to call colony collapse disorder, was unprecedented in its severity and its magnitude. By June of 2007, remember it started in November 2006, colony collapse [disorder] had been reported in at least 35 states. People were quite concerned. In fact there was a meeting for scientists that work on bees to prioritize research to figure out what was going on. The scientists thought the most likely explanations were a new disease, maybe pesticide poisoning—Bees are very sensitive to pesticides; ill health due to management—being put on trucks and driven across the country—or just poor nutrition. Beekeepers are feeding their bees high fructose corn syrup, which is the stuff you drink in Coca-Cola, not so good for bees either. What did the public think? What didn't the public think? [Various] explanations offered for disappearances included and not limited to genetically modified corn pollens, cell phones, Wi-Fi, elevated carbon dioxide, elevate ultra-violet light, Osama Bin Laden, automobile growth, solar maxima, jet chemical contrails, mutant bee cannibalism, fluctuations in the Earth's magnetic field, radiation from Chernobyl, alien abduction—those were the explanations that nobody had any evidence for.
So, it's really important for scientists to get together and use modern tools to solve this mystery. And in fact, these are forensic tools, just like you see on the show CSI, in fact Gil Grissom, the character on CSI, the head forensic scientist, is an entomologist by training and in this episode he goes to a crime scene and he starts working on colony collapse disorder. In fact a lot of us were tuned in the CSI to figure out if Gil Grissom could solve this. So [we] don't exactly know how he went about it, but we know that there are all kinds of tools for forensic investigation. Forensic is just a word that mean[s] "legal" or "law", but a lot of people use forensic in the context of investigating death, so that's what we were doing. Deaths or disappearances, and we had, there are all kinds of tools for investigating mysterious deaths or disappearances, but they are all made for humans; they are no[t] easily translated to working on bees. Among other things, what does Gil Grissom and his crew always do? They talk to people. Well, we couldn't talk to the bees, we couldn't really even check the bodies of the victims because there weren't any bodies. But we could use some of those tools, like a microscope, very basic tool[s]. and it was very clear using a microscope, honeybees have all kinds of problems. Varroa, it's a parasitic mite, it sucks the blood of bees particularly when they're in the pupal stage, when they are metamorphosing or transforming from a grub to an adult, they can't move, they're sealed in their little waxed cells; and the mite is sucking its blood and the bee is helpless. So, can you imagine some creature on your body that's about the size of a lobster sucking your blood, so [it's a] very serious pest and it's particularly a pest, because just like mosquitoes can spread viruses like yellow fever as they suck blood, Varroa mites can spread viruses to bees. Eighteen different viruses affect bees. So the thought was maybe Varroa, which has been here in the U.S. since the 1980s, brought in a new virus. And sure enough using molecular techniques, a new virus was discovered. It was called Israeli Acute Paralysis Virus. it's only been known since 2004; it was described in Israel. But it wasn't quite right. It's called Paralysis Virus because the bees are paralyzed, but these bees weren't paralyzed—they were gone, they disappeared. But it was found in 83 percent of the colonies that were afflicted. However, biologists went into their freezers and collected samples that were healthy from years before CCD and they found this virus. So it can't have been Israeli Acute Paralysis Virus unless the virus mutated, because it's been here all along, we didn't just didn't know it was here. So more investigation with more microscopes turned up another disease of bees. This time it's a fungus. There are two types of fungi that infect bees. They're called nosema, and Nosema ceranae is a new virus that's been here since 1995; [it] basically turns the bees to goo. And they found it in a hundred percent of the sick colonies. [So] that's it, right? No, it's not: They found it in 81 percent of the healthy colonies. So the first few months of investigation, people kept finding things wrong with bees that were not the explanation for CCD. But what about pesticides that [are used] to control those mites? Beekeepers have been using pesticides in the hive. A pesticide is something that kills an undesirable organism, and a mite, is very closely related to a bee. So a chemical that kills a mite is very likely to kill a bee, too. So it's very hard to find a pesticide that kills only mites and not insects. Mites are arachnids, bees are insects. But they use one [pesticide] called Apistan; it's been in the hive, maybe that's what causing problems—they are sensitive to the pesticide. Moreover, bees fly through all kinds of agricultural fields and are exposed to all kinds of pesticides. Maybe it was a new pesticide that was causing these problems. And in fact there is a new pesticide; it's only about ten years old, a group called the neonicotinoids. Everyone knows what nicotine is, right? It's in tobacco, it's a nerve toxin, it's a neurotoxin. Kids: Don't smoke, it actually screws up your nervous system. Well that's what this new pesticide did, and people in France, beekeepers in France were convinced that this was causing [the] mysterious disappearances of bees. It actually causes brain damage in bees. It makes them forget. What does a bee have to remember? Well the way home among other things, So the bee keepers in France were absolutely convinced it had to be this new pesticide, Imidacloprid. It's got a long name called Imidacloprid, and they banned it for use in sunflowers, a big crop in France. Bees love sunflowers. The neonicotinoid, the Imidacloprid, shows up in the pollen and nectar. The French beekeepers thought, "That's how they are getting poisoned; we'll ban this pesticide." What about in the U.S.? Well France banned the pesticide; they still have colonies disappearing. Imidacloprid has been here for ten years. Why didn't it cause disappearances? And finally, when chemists started using another forensic technique, a machine called a GC mass spect, Gas Chromatograph, looking for pesticide residues in the afflicted colonies, they found only three out a 108 pollen samples with this chemical that was suspected. Well that can't be it either. So, we can almost just about rule out the Israeli Acute Paralysis Virus, the nosema fungus, the neonicotinoid pesticide. Well we're narrowing things down, but we still don't know what it is. Well in October 2006, right before colony collapse disorder hit, a new tool became available for forensic investigation and that's the honeybee genome. The genome is the genetic blueprint, the DNA instructions for making an organism. And the whole thing, all 10,000 genes in a honeybee genome, were all sequenced and annotated and available. So this is my student Reed Johnson who's the first person to use new molecular methods to find out what was going on inside the bees by looking at their genes. And he used a technique called microarray, whole genome microarray. It's a little glass slide that has little dots on it, little dots of DNA. Each dot corresponds to one gene. Every single gene in the honeybee genome is on that slide. So what you can do is use this microarray, [this] little array, to see which genes are being turned on and which are turned off in the honeybee. It's called gene expression—whether a gene is turned on or turned off. The idea is, if they are exposed to a pesticide, the genes that code for enzymes that break down pesticides will be turned on. If they're exposed to a new disease their immune genes will be turned on, just like if you're exposed to a disease, your immune system gets activated. So Reed looked at the microarray of healthy bees and sick bees and colony collapse disorder bees to see if there was a difference in which genes were turned on and which were turned off. He compared healthy bees, and that was hard; we didn't know where the healthy bees were. So we actually had to use bees from the freezer from 2004 and 2005 to absolutely know that they didn't have CCD, because there was no CCD then. He ground them up, extracted their DNA with their genetic material, and looked to see which genes were turned on [and] which were turned off. What did we find? A lot of genes. So we looked for the genes that were expressed differently in healthy bees and in colony collapse disorder bees and we found a mixture. We found that some other genes for detoxifying pesticides were turned on, some were turned off, some of the genes that help bees fight off pathogens were turned on, others were turned off. And the biggest, most definitive category that we found clearly associated with colony collapse disorder, we don't know what those genes do. But we know that they are markers for the disease, for this phenomenon, and [when] we figure out what those genes do, we'll know what's causing colony collapse disorders. So, we haven't ruled out any of the possibilities, but now we do have some tools, some molecular tools we can use to diagnose colony collapse disorder. We can do that by looking for those gene fragments that we know are only turned on in the sick bee[s], the colony collapse disorder bees. A beekeeper will have more time to prepare and protect his bees and maybe not suffer such catastrophic losses. Our beekeeping industry lost about a third of its bees between 2007 and 2008. Now anybody who watches CSI knows that Grissom can wrap these things up in two episodes, max. So here we are, it's been since October 2006, [and] we still don't know exactly know what's going on. There are lots of people working on this. We have the genetic footprint of colony collapse disorder, and we're trying to figure out what it is. The next question is: How can you help? How can you help stop these losses. Well, we plant acres and acres and acres of one particular crop. Bees are used to going from one flower to another; they feed on hundreds of different flowers. We've changed the landscape so and kept things so free of weeds, there's nothing for them to eat. So one thing you can do is plant a garden, plant flowers, plant food for the bees. Another thing you can do is don't be afraid. People have very mixed feelings about bees. Yes at one end there is a stinger; yes, they can sting if you disturb their hive—that's the only reason they'll sting or, if you step on them by accident. But each bee can sting only once; then she dies. They're not particularly anxious to inflict pain on you. They will be perfectly happy if you go away. Learn to appreciate bees, just keep your distance, they won't bother you if you don't bother them. And if you look at them as your allies and not as your enemy that also will help the bees. Finally, you could be a beekeeper. It's not so hard, universities all across the country offer courses; you can order the materials, and you can be [the] first person on your block to have 30,000 pets.
Steve: So you see the mystery of colony collapse disorder has not been completely solved. Now just last week, a review paper was published in the journal Public Library of Science ONE that makes the case that the disorder is caused by the interaction of pathogen[s] such as the fungus or mites and other stress factors. The genome work of Reed Johnson and others could eventually help to nail down a more exact mechanism and point the way to a strategy to stop the bees from vanishing.
In the next episode you'll hear more about and from May Berenbaum—for example, how she's the inspiration for the memorable X Files character—and you'll hear from John Williams, the beekeeper at Darwin's home in England. Plus, we'll test your knowledge about some recent science in the news. Till then, for Science Talk, the weekly podcast of Scientific American, I'm Steve Mirsky. Thanks for clicking on us.