Colony Collapse Disorder: Is a Pair of Pathogens to Blame for Honeybee Decline?

A bee researcher and professor at the University of Montana discusses his new research on the massive honeybee decline called colony collapse disorder.

Honeybee on White Background

Honeybees play a key role in pollinating important crops. The mysteriously declining population may have dire agricultural consequences.


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Colony collapse disorder (CCD) research continues to be a controversial subject. The New York Times published an article in October, which we reference in this article, with a title suggesting that the work of Jerry Bromenshenk and his team had uncovered the definitive cause of CCD: Scientists and Soldiers Solve a Bee Mystery. However, upon preparing this article for publication, we discovered an article calling into question Jerry Bromenshenk’s findings (see CNN Money’s What a scientist didn’t tell the New York Times about his study on bee deaths). While Bromenshenk’s research on honeybee decline is compelling, his findings have been a matter of debate among experts. To learn more about the many possible causes of CCD, view MOTHER EARTH NEWS’ page dedicated to honeybee decline. 

Honeybee decline has been a puzzling problem for farmers and entomologists alike since 2006, when honeybees began mysteriously dying in large numbers. Scientists have been scrambling to discover the cause of what has been termed colony collapse disorder (CCD) over the last few years, but no official cause has been determined.

Theorists have blamed everything from cell phones to Roundup for the declining honeybee population, and an intriguing study published in October suggests that the culprit could be a combination of a powerful virus and lethal fungus. We caught up with Jerry Bromenshenk, a professor at the University of Montana and lead researcher on the bee study linking CCD to these pathogens.

How did you get involved in bee research? 

I am an entomologist by training, originally working with grasshoppers and the damage that grasshoppers did to the grasses of rangelands.

In the 1970s, after the Arab oil embargos, coal mines in the West were opened and coal-fired power plants constructed and brought online. There was considerable interest in the potential bioenvironmental impacts of this development on semi-arid rangelands. I was hired on a post-doctoral position to look at impacts to insects. I found around 6,000 colonies of bees near the Colstrip, Mont., power plants and decided that I had to include beneficial insects such as bees in my investigations.

Many people think about bees as pests. Why should we be concerned about bees dying? 

People mistakenly call the vespids — wasps, hornets and yellow jackets — bees. They are the flying/stinging insects that visit your picnic table and attack when you are near their nests. Honeybees are not even in the same family as the vespids, and they are as distinctly different from the vespids as are ants. You’d never confuse an ant with a bee, but people often confuse bees with wasps. Most bees can’t even sting.

Honeybees will defend their homes. When foraging, they are not defensive, and they apparently can’t smell sugar, so they seldom visit a picnic table. If you get stung and don’t see a stinger, it is not a honeybee. The honeybee leaves its stinger behind, and it then dies. So, it is not in the best interest of the bee to sting you. They usually try to scare you off.

With respect to the second part of your question, we need to be concerned about bees because they not only produce honey and wax and other useful products, but they also pollinate many of the plants that provide the food we eat.

What is it specifically about CCD research that you think is so interesting and important? 

CCD strikes hard and fast. From the very first beeyards that we saw, CCD appeared to be contagious, moving from beekeeping operation to beekeeping operation, sweeping from one end of large stockpile beeyards to the other.

Yet, there were no visible signs of any known disease. For example, it is relatively easy to see foulbrood, mites or known signs of virus problems such as deformed wings or sacbrood. None of those correlated well with CCD.

What is the world facing if the cause behind CCD isn’t discovered and the problem isn’t solved? 

Almost all fruits, nuts and vegetables either benefit from or are dependent upon insects for pollination, and the majority of that pollination is accomplished by honeybees. Worldwide, there have been substantial declines of the numbers of insect pollinators.

The number of honeybee colonies in the United States has been decreasing. At this point in time, we can barely marshal enough bees to cover some of our largest crop acreages. Much of the loss in numbers of honeybee colonies is a reflection of fewer and fewer beekeepers — the loss of beekeepers is a critical issue. However, problems like mites, Africanized bees and CCD are all factors that tend to discourage new beekeepers.

If we can’t solve CCD, the availability and diversity of quality produce is likely to decline and we will become more dependent on food that is shipped in from overseas.

Of course, CCD might just disappear, but I’m not expecting that to occur.

Your research reveals that bees may be taking a “one-two punch” from a virus and a fungus. Is it possible that one of these maladies — either the virus or the fungus — could be responsible, alone, for killing this large number of bees? 

Our inoculation trials indicate that either pathogen could kill large numbers of bees, but the lethality increases when the two are combined.

How has research collaboration with the military enhanced your ability to study CCD? 

The Army brought an innovative new technology to the search for a possible pathogen with respect to CCD. They did all of the sample analysis. Robert Cramer at Montana State University did confirmatory studies withnosema(a lethal fungus that may be endangering bees), as well as the inoculation trials.

Without the Army’s technology (courtesy of the U.S. Army Edgewood Chemical Biological Center), we would not have discovered any of the three new viruses that we found, nor the statistically significant correlation of the fungus and the virus in colonies collapsing with CCD.

At this point, you haven’t been able to nail down a causal relationship between these pathogens and dying bees. How will your future research uncover whether the pathogens are causing widespread collapse, or if dying bees are more susceptible to them? 

We are seeking funding to extract, isolate and purify the iridescent virus in CCD colonies so we can repeat the inoculation trials with the fungus, the virus, and the fungusplus the virus. We need to introduce these pathogens alone and together into whole, healthy colonies of bees. If we induce CCD, we then need to recover the pathogens. If we can accomplish that, we will have met the requirements of an approach called Koch’s Postulates — a standard means of verifying pathogens as causal agents.

We also need to look at factors that may trigger the expression of one or both of these pathogens. We know that they tend to thrive in cool, damp conditions and that both are found in the gut of the bee. That implies that nutrition may be another factor influencing the susceptibility of bees — it is something we can test.

How has your research been funded? 

Our work was done on a shoestring budget. The Army contributed the analyses. Beekeepers and beekeeper associations provided small grants — groups like the National Honey Board, Almond Board of California, Project Apis m. and others.  Most of the authors contributed their time. We did not receive any of the USDA’s CCD funding. (See the complete funding list in the PLoS ONE article.)

In the past few years, researchers have pointed to numerous potential causes of CCD, and many of those have been disproved or reconsidered. Is CCD a particularly difficult case to solve? If so, why? 

It is difficult to solve because it doesn’t leave bodies for autopsy — the bees of most interest disappear. The movement of more than a million colonies of bees across the nation and back and forth through agricultural lands makes tracking almost impossible. When and where it will appear and for how long are equally impossible to predict. Many factors such as viruses and pesticides cannot be examined without costly instrumentation.

There is a new technology, again derived from the military, that is available to beekeepers for rapid and relatively inexpensive screening for viruses. It is called the Integrated Virus Detection System, and the service is being provided by a small business in Montana that has a technology transfer agreement with the U.S. Army. That business is BVS Inc. in Florence, Mont. It is owned and operated by Mr. David Wick.

MOTHER EARTH NEWS has been reading about research that may link pesticides to CCD. What are your thoughts about that relationship? 

We did not have any funding to look at pesticides and CCD. Others, such as investigators at Penn State University, were funded to do that work. I’ve just returned from several beekeeping association meetings in the United States and Canada, and there were several reports by students and senior scientists who are looking at pesticides and impact to bees, especially sublethal impacts.

Our study did not look at pesticides. We barely had enough funding to do the pathogen work, and the instrument that the Army used wasn’t set up to look for pesticides. The Army’s instrument provided us with a rare opportunity to obtain an unrestricted survey of pathogens in bee colonies. That was the focus, and the core data was provided by the Army.

We really don’t know how or if pesticides may interact with the pathogen pair that we found. Obviously, the expression of this duo is likely to be triggered by other stress factors such as nutrition, weather, general health and possibly pesticides.

MOTHER EARTH NEWS has been tracking the progress of colony collapse disorder and the research attempting to determine a cause. Visit our list of articles and links related to honeybee decline to learn more. 

Lindsey Siegele is the Senior Web Editor at Ogden Publications, the parent company of MOTHER EARTH NEWS. Find her on .

1/1/2011 11:09:15 AM The impact of neonicotinoid insecticides onbum blebees, Honey bees and other non-target invertebrates (revised version) Vicky Kindemba 2009 October 2009 ISBN 978-1-904878-964 Edinburgh ...and then the interesting speculation: africanized honey bees are for all intents and purposes european honey bees (no more difference than between human races), the assault on them began about the same time as CCD. Honey bees like corn pollen and transport it off far and wide, maybe even from non-gmocorn to gmocorn. Might this cause problems for monsanto seed growing? What is the best way to keep gmo-crops free of *wild* pollen? The epa imidacloprid studies were done on rape --changed from corn-- and has confounds (in the scientific sense). Bees don't prefer rape pollen, the rape fields were too small, the bee treated/non-treated foraging ranges overlapped.

1/1/2011 10:20:05 AM

bees... ccd... epa... Germany, Italy and France have already banned Clothianidin why hasn't the EPA? "EPA Memorandum PC Code: 044309 Date: November 2nd, 2010 SUBJECT: Clothianidin Registration of Prosper T400 Seed Treatment on Mustard Seed (Oilseed and Condiment) and Poncho/Votivo Seed Treatment on Cotton. page 2 par 1 Clothianidin’s major risk concern is to nontarget insects (that is, honey bees). Clothianidin is a neonicotinoid insecticide that is both persistent and systemic. Acute toxicity studies to honey bees show that clothianidin is highly toxic on both a contact and an oral basis. Although EFED does not conduct RQ based risk assessments on non- target insects, information from standard tests and field studies, as well as incident reports involving other neonicotinoids insecticides(e.g., imidacloprid) suggest the potential for long term toxic risk to honey bees and other beneficial insects. "The British Beekeepers' Association has today announced plans to end its controversial practice of endorsing pesticides in return for cash from leading chemical manufacturers.The endorsement of four products as 'bee-friendly' in return for £17,500 a year caused outrage among many beekeepers because one of the companies, Bayer Crop Science, makes pesticides that are widely implicated in the deaths of honeybees worldwide."

12/20/2010 10:05:18 PM

I once read (many years before this form of CCD was reported) about one type of Queen bees that invade a hive as their "smell" is more neutral than another invading bee species. It sounded just like CCD we hear of today. I don't remember if they were South American or South African Bees. Since the new queens don't trigger the original queen to attack, she is treated by the drones like the original queen all the while they are there. The eggs that the new queen lays become queens just like her, and also begin laying eggs in that hive. Eventually they replace so many of the drones that the food consumption by all the new queens exceeds the supply taken in by the remaining drones and the colony collapses. The new swarm of invader Queens spread out and look for other hives to invade. Has anyone thought to look into if this could possibly have anything to do with the CCD? All it would take is one successful queen to get into one hive, and then we transport them all over the USA!

alexey chudakov
12/20/2010 7:46:22 PM

I did see how beekeepers, who had less than 200 hives claimed lost of 450-500. They presented empty hives to get support from government. This is why You will never see there dead bees. Some beekeepers place beehives right on the ground,humidity and ants force families to leave the hive in summertime. I worked on commercial farm in Israel and know how it suppose to look like. If bees leave hive its beekeeper's fault.

t brandt
12/19/2010 9:02:26 PM

a] The honey bee is, afterall, an invasive species in NA. As its numbers decline, don't the numbers of its native competitors re-bound? b] Has anyone studied the natural population dynamics of the honeybee? Could this decline, for which no culprit is obvious, be merely a manifestation of natural cyclicity of numbers. The 17 yr cicada would be an extreme example of such a phenomenon. c] How big an economic probelm is it really, given that the crops taking up the most acreage in NA (corn, beans & wheat) are all wind pollinated anyways?