Actor Charlie Sheen is urging his 8 million Twitter followers to vote for California Proposition 37, which would require labeling of food that contains genetically-modified organisms. He implies that this measure would help restore honey bee populations, which have shrunk in recent years.

Why are bees vanishing? Are genetically-modified organisms (GMOs) responsible, as Sheen asserts?

Back in April 2009, Scientific American wrote a lengthy article addressing the issue. The article was based on analysis by an inter-disciplinary team of experts from government and academia. If you want to read the whole thing, you have to pay for it, but here’s the relevant part:

One theory favored by many concerned citizens was that bees could have been poisoned by pollen from genetically modified crops, specifically the so-called Bt crops. Bt crops contain a gene for an insecticidal toxin produced by the bacterium Bacillus thuringiensis. When pest caterpillars feed on crops producing these toxins, they die. But already before the onset of CCD [colony collapse disorder], research had shown that the Bt toxin becomes activated only in the guts of caterpillars, mosquitoes and some beetles. The digestive tracts of honeybees and of many other insects do not allow Bt to work.

The growing consensus among researchers is that multiple factors—such as poor nutrition and exposure to pesticides—can interact to weaken colonies and make them susceptible to a virus-mediated collapse. In the case of our experiments in greenhouses, the stress of being confined to a relatively small space could have been enough to make colonies succumb to IAPV [the Israeli acute paralysis virus] and die with CCD-like symptoms. More recent results from long-term monitoring have identified other unexpected factors for increased colony loss, including the fungicide chlorothalonil. Research is now focused on understanding how these factors relate to colony collapse.

The notion that pesticides may be responsible seems to be gaining currency:

A widely used farm pesticide first introduced in the 1990s has caused significant changes to bee colonies and removing it could be the key factor in restoring nature’s army of pollinators, according to two studies released Thursday.

The scientists behind the studies in Europe called for regulators to consider banning the class of chemicals known as neonicotinoid insecticides. In the U.S., the Environmental Protection Agency told that the studies would be incorporated into a review that’s currently under way.

A pesticide trade group questioned the data, saying the levels of pesticide used were unrealistically high, while the researchers said the levels used were typical of what bees would find on farms.

The jury is still out about neonicotinoid insecticides, but two things seem clear. First, GMOs aren’t the culprit for vanishing bees. Second, Charlie Sheen is full of it.

But it gets worse. Sheen also tweeted that GMOs have been linked to tumors:

The implication is that genetically-modified food is putting all of us at risk of cancer. Scary!

We’re guessing the claim is based on a much-hyped French study published in September which showed that rats fed Roundup Ready® corn developed cancer at higher rates than control rats fed non-GMO corn. The researchers, however, have come under intense criticism for poor methodology and shady research practices. Here’s what one plant biotechnology researcher said about the study:

“There is very little scientific credibility to this paper,” said Martina Newell-McGloughlin, a plant biotechnologist at the University of California, Davis. “The flaws in the test are just incredible to me. To be totally honest with you, the type of statistical analysis they used is really a type of fishing expedition. One individual referred to it as ‘fantasy statistics.'”

Fortunately, the scare tactics used by Sheen and other proponents of Proposition 37 do not appear to be working. Polls show support for the ballot initiative plunging.