By David R. Tarpy,
North Carolina State University Extension Apiculturist

This article first appeared in the 2012 summer edition
of the North Carolina State Beekeepers’ Association’s Bee Buzz.

Honey bees have always been a source of fascination yet trepidation for humans throughout our history. This stems in large part because they do not fit neatly into most categories. Bees are not domesticated animals—as they are free flying and live as wild creatures—but they are still managed and shepherded by beekeepers. They do not fall under the strict umbrella of agriculture—as they are technically a service industry to agriculture—yet they are still vital for ~35% of our food supply through pollination of over 100 crops.

Perhaps in part because of these fuzzy boundaries, the media often has similar trouble in trying to portray honey bees. This difficulty is no better apparent than in the media’s portrayal of honey bee science in general and research on Colony Collapse Disorder (CCD) in particular. The main goal of the media is to communicate—in fairly simple and straight forward language—something newsworthy to the general public. When it comes to recent findings dealing with honey bee health, these reports can actually be oversimplified, where anything dealing with honey bee mortality is immediately equated with CCD. This is just simply not the case! Rather, the health of the honey bee population, and the scientific evidence that investigates mechanisms behind ill-health, lies on a continuum ranging from poor anecdotes on one end and strong empirical data on the other. The media often cannot or fails to portray this subtle yet fundamentally important nuance.

Let’s take a couple of examples in the past year that spans this range of high- to low-quality scientific evidence as they are portrayed in the media. In each case, both the scientists and the media claimed the findings to explain the underlying reason behind CCD. Fairly recently, a paper was published in the highly prestigious US journal Science by a French research team titled “A common pesticide decreases foraging success and survival in honey bees,” which gained fairly widespread media coverage. The researchers fed honey bees sub-lethal doses of a neonicotinoid pesticide (which have long been questioned to be involved in bee ill-health), recorded foraging behavior by measuring the rates of returning field bees, and mathematically modeling the effects on colony populations. They showed quite convincingly that pesticide-fed bees were less likely to return to the colony than untreated controls, and that this could theoretically effect colony populations over time. However, the study did not actually measure colony decline (but rather mathematically projected the effects on colony health), did not include a third treatment of bees treated with another toxin (known in scientific parlance as a ‘positive control’) to see if all poisoned bees have an increased mortality compared to the pesticide in question, and the mathematical model suggested that it would only affect colony population over the course of several months (not several days, as in the hallmark symptom of CCD). Thus this study provides important evidence towards the long-term struggle against agricultural insecticides, but there are clearly other important pieces to the puzzle to explain how neonicotinoids are linked to CCD.

Another study came out a couple of months ago, and I’m fairly sure you heard about it: “zombie flies.” This media story was based on a scientific article by a research team at San Francisco State University who reported a curious parasitoid of honey bee foragers. This potential pest is the phorid fly Apocephalus borealis, which is known to parasitize bumble bees, but the reported results demonstrate that it can also infect and eventually kill honey bees. It turns out that this “host switching” from bumble bees to honey bees was reported as far back as the 1980s, and there remains many questions about how widespread and impactful these flies might be on colony health. For example, all of the earlier studies that investigated colonies that were actually afflicted with CCD showed no trace of these parasitoids, and the population densities of flies required to create catastrophic apiary mortalities would be astronomical. Clearly, more needs to be done on this topic before there is any strong linkages with global honey bee mortality, let alone CCD.

Perhaps the greatest example of scientific oversimplification is a short article in Current Science by a research group out of India. They observed honey bee foragers being attracted to—then dying in—disposable paper coffee cups, where foraging bees collect the discarded sweetened liquids but then drown. From this, the authors make the following argument: “There are about 1.3 billion and 800 million cups of coffee and tea consumed daily around the world by using millions of disposable cups. This may lead to bee collapse in future and reduction in agricultural productivity throughout the world.” I find this dubious logical connection to be, to say the least, ridiculous. Next time one of your colonies die, check your trash!

CCD is indeed a cause for concern, but I believe that it is imperative to place honey bee mortality into the greater context of why honey bee colonies die overall (Figure 1). Over the last 5 years (for which we have the best data), about one-third of the US honey bee population has died over the winter. In most cases, these losses can be explained by known factors, such as varroa mites or other management issues (e.g., starvation, problems with queens, known pesticide poisonings). In about of quarter of these cases, however, these losses are genuinely unexplainable, as none of the usual suspects can be conclusively linked to mortality. Of these, only a subset are attributed to CCD sensu stricto (that is, they fit all of the defined symptoms of the syndrome). So in the end, only a fraction of the 2.3 million managed honey bee colonies in the US have died with “CCD-like symptoms,” which leaves the vast majority dying from many other causes. As such, honey bees die from many things, so the media (and particularly honey bee scientists) should not equate CCD with all honey bee mortality.

The take-home message: the best way to maximize colony health is to focus on the enemies that we know: keep your varroa mites in check and ensure proper nutrition (things over which we have control).

Looking at the entire puzzle, with each piece representing a different scientific study, it is abundantly clear that colony mortality is the product of multiple factors, both known and unknown, acting singly and in combination. Thus there is no “one” cause (or solution) to CCD specifically or honey bee ill-health generally. Honey bees are complex, as is our management of them, so we should not blindly believe any over-simplification of honey bee research that attempts to explain global colony mortality. Rather, we should collectively and rationally try to fit all of the pieces together to gain a better perspective. As beekeepers, we inherently understand this complexity, and so our portrayal of apiculture science should do the same. So the next time you read the latest sensational headline, just remember—caveat lector.