Worker bees ripen honey by adding digestive enzymes to nectar, heating the solution to detoxify plant defensive compounds, and evaporating off excess water.

Forgive the off-topic post, but today is Food Day here at Scientific American. As I teach a university beekeeping class, I'd like to talk about honey.

Considering the revered place of honey as the oldest natural sweetener, and considering that its insect makers- honey bees- are highly intolerant of pesticides, you might think honey would be the easiest food crop to produce for the "organic" food market. But you'd be wrong.

Here is the primary problem in map form:

The long reach of the superorganism: a typical foraging radius of a honey bee colony normally stays within five kilometers of the hive (marked by the red circle), but during times of dearth bees will fly more than twice as far in search of resources.

Honey is floral nectar cooked down into a thick carbohydrate soup. How many flowers are needed to make honey? A lot. More than most of us can easily comprehend. To survive a year, a single colony brings in about 250 pounds of nectar- an astounding weight for a small insect. It's not as though individual flowers are generous with nectar, either. Most yield just the smallest of droplets. A standard jar of honey from the supermarket requires bees to make a million flower visits. A colony might produce 50 to 100 such jars per year.

Thus, a colony's foragers cover a staggering amount of territory. Because bees are furry, statically attractive little animals (useful for pollen collection), their bodies readily gather all sorts of environmental particles. Any agrochemical applied anywhere within a colony's extensive reach can end up back in the hive. Since beekeepers don't own the tens of thousands of acres surrounding their hives, they have no control over what their bees are bringing home.

Organic honey isn't impossible. It's just beyond of the ability of most beekeepers. Bee yards situated in isolated spots deep in the Adirondacks, or mountain valleys in sparsely-populated New Mexico, can probably pull off honey free of agrochemicals. Most beekeepers operate within a bee's flight of pesticides, however, making "organic" honey an illusory proposition.

Then there is a second, more insidious problem. The hydrocarbon chains of beeswax itself retain certain pesticides, including those used by conventional beekeepers against the ubiquitous Varroa mite. Over time pesticide residues accumulate in the combs, so chemicals linger or build for years beyond the original applications. By itself this might not present a problem for aspiring organic beekeepers, except that beekeepers routinely buy and sell wax as starter comb. A recent survey of pesticides in commercially-available beeswax recorded an astounding 98% of samples contaminated with miticides. An organic beekeeper who refrains from chemical pest control and situates her hives somewhere off in the wilderness is still going to have pesticide contamination unless she also abstains from using the omnipresent (and very useful) wax starter foundation.

Certainly some of the honey labelled as "organic" may actually lack pesticide traces. But I'd not count on it. None of the certification protocols take into account the newly-documented problem of wax contamination, and most underestimate the real foraging radius of a large bee colony.

As to whether agrochemical-free honey is significantly healthier for humans, that's a contentious debate I'm all too happy to sidestep.

source: Mullin CA, Frazier M, Frazier JL, Ashcraft S, Simonds R, et al. (2010) High Levels of Miticides and Agrochemicals in North American Apiaries: Implications for Honey Bee Health. PLoS ONE 5(3): e9754. doi:10.1371/journal.pone.0009754