Is corn syrup killing the honeybees?

A trio of recent studies faults a common family of corn pesticides for disorienting honeybees, potentially leading to colony collapse disorder. The German chemical company Bayer, which manufactures the pesticides, disagrees.  

Reuters / Vasily Fedosenko
In this image a bee is hovering above a Marigold flower. Recent studies have found ways that even low doses of widely used pesticides can interfere with the memories and homing abilities of harm bumblebees and honeybees.

Since 2006, something awfully strange has been happening to North America's commercial beehives. Beekeepers are finding that many of the boxed hives ranged throughout their apiaries have been inexplicably abandoned by worker bees. These ghost-hives typically have ample stores of honey and pollen, and hold gestating colony broods, sometimes even a lone queen.

This phenomenon is called Colony Collapse Disorder (CCD), and two papers published recently in the journal Science say that it is correlated with the presence of a ubiquitous class of insecticide called neonicotinoids. A newer study published in the Bulletin of Insectology suggests that this insecticide is introduced into bee colonies through, strangely enough, high-fructose corn syrup.

The insecticide was developed by Bayer AG, the German chemical and pharmaceutical giant most recognized for its original brand of aspirin. Today, the $53 billion company has released a rebuttal to the suggested link between neonicotinoids and Colony Collapse Disorder.

The population of feral honeybees in the US has been steadily decreasing for the past half-century, and is now almost nonexistent. In the same timescale, commercial honeybees experienced a shallower decline in population. However, since 2006, they have started rapidly disappearing in North America and Europe. Many scientists agree that the confluence of factors that drove population decline before 2006 is still in effect, but that something probably changed in light of the new rash of colony collapses.

Identifying the causes of CCD is a complex proposition, but the disorder's symptoms and effects are quite simple. It usually occurs when worker bees first depart their hives to forage, in winter or early spring. Then they don't return. Their hives typically have an active queen, ample food, and a developing brood – not exactly the home a bee would abandon under normal circumstances. Many scientists have since suggested that pesticides may disorient bees or affect their memory, making them unable to navigate home.

Chensheng Lu, an environmental scientist at Harvard and the lead author on the Bulletin of Insectology paper, was curious as to how the insecticide may be introduced into the colony, and decided to investigate high-fructose corn syrup, which for the past decade has been used by beekeepers to supplement hives that have been decanted of honey. Much of the US corn crop is treated with neonicotinoids, and so trace amounts of the insecticides can often be found in the sugary syrup.

Lu and colleagues designed an experiment that would expose hives to concentrations ranging from 20 to 400 parts per billion. Within 4 months, 15 of the 16 experimental hives had been emptied by what appeared to be CCD, according to the researchers.

As more studies are published on this subject, the link between neonicontinoids and CCD may become more apparent. In this case, Bayer AG could only be held indirectly accountable, as it is the beekeepers who are substituting the inexpensive syrup for bee honey, thereby introducing the pesticide.

Earlier today Bayer released a statement that criticized the Harvard study, asserting that the sample size was too small to be statistically significant and that the "authors ignored the scientific consensus that bee health is impaired by multiple factors, including inadequate diet, pests and parasites such as the varroa mite, microbial diseases, mismanaged colonies, and loss of genetic diversity."

These are not unreasonable criticisms. Though the study authors certainly didn't "ignore" a "scientific consensus" on the multiple factors that could cause CCD. They simply investigated one of them. Nonetheless, scientists are still puzzled by the many possible causes of the disorder. They're also concerned, and for good reason.

The common honeybee is widely recognized as the most important insect pollinator. They're extremely versatile, able to collect both nectar and pollen and to transport it. They are easily managed by beekeepers, and live year-round, which means they will service a wide variety of plants. They're also fecund; one simple colony can consist of one queen, a few hundred drones and roughly 80,000 workers. There is no realistic scenario in which we could operate our mass-scale farms without them.

Bayer's concerns about the studies are not all that surprising considering the company's financial interests. But if more research confirms that its neonicotinoids are afflicting the commercial honeybee population, then they are threatening an enterprise on which Bayer crucially depends: agriculture itself.

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