(Beyond Pesticides, April 1, 2011) A British government scientist on Wednesday announced that he has ordered a review of a class of pesticides known as neonicotinoids, to determine what effects they may have on bee and pollinator health. Neonicotinoids, such as clothianidin and imidacloprid, have come under intense scrutiny recently due to concerns regarding their toxicity to honeybees, which are essential for a secure food supply in their role as crop pollinators. This has led some to suggest that chemicals such as these could be contributors to honeybee Colony Collapse Disorder (CCD).
According to the London Daily Mail, the chief scientist at the UK Department of Environment, Food and Rural Affairs (DEFRA), Professor Robert Watson, has directed DEFRA scientists to reexamine findings on neonicotinoids and their effects on bees. The Mail suggests that Watson may have been partly motivated by a recent study done by Dr. Jeffrey Pettis of the U.S. Department of Agriculture’s Agricultural Research Service. This study was the first to show that neonicotinoids impact the survival of bees at levels below the level of detection, meaning that field studies would not have considered the role of the pesticide, because they would not have detected it.
Although a spokesman for DEFRA has dismissed the new evaluation as little more than a routine review, Watson was quoted in the Mail as saying “I’ve got people in the bee-health pollinating area and people in pesticides to review the literature for me and to come back to me exactly on this issue. It’s clear that we have to be concerned generally about bees and other pollinators. There is a genuine concern that if indeed there were to be a serious decline in the various pollinators, it could have implications for agriculture, no question.”
After discovery of a leaked memo from the U.S. Environmental Protection Agency in December 2010 citing a flawed study on precisely this issue, Beyond Pesticides along with beekeepers and other environmentalists, called on EPA to remove the neonicotinoid pesticide clothianidin from the market. EPA responded by defending clothianidin and the agency’s pesticide review process, saying that they “are not aware of any data that reasonably demonstrates that bee colonies are subject to elevated losses due to chronic exposure to this pesticide.”
Clothianidin and imidicloprid are members of the neonicotinoid family of systemic pesticides, which are taken up by a plant’s vascular system and expressed through pollen, nectar and gutation droplets from which bees then forage and drink. Neonicotinoids kill sucking and chewing insects by disrupting their nervous systems. Beginning in the late 1990s, these systemic insecticides began to take over the seed treatment market. Clothianidin is Bayer’s successor product to imidacloprid, which recently went off patent. Both are known to be toxic to insect pollinators, and are lead suspects as causal factors in CCD. Together, the two products accounted for over a billion dollars in sales for Bayer Crop Science in 2009. Imidacloprid is the company’s best-selling product and among the most widely used insecticides in the U.S. Starting in about 2004, seed companies in the U.S. began to market seeds treated with a 5-X rate of neonicotinoids (1.25mg/seed, compared with the traditional 0.25 mg/seed).
Colony Collapse Disorder is the name given to the mysterious decline of honeybee populations around the world beginning around 2006. Each winter since, one-third of the U.S. honeybee population has died off or disappeared (more than twice what is normal). While CCD appears to have multiple interacting causes including pathogens, a range of evidence points to sub-lethal pesticide exposures as important contributing factors. Neonicotinoids are a particularly suspect class of insecticides, especially in combination with the dozens of other pesticides found in honeybee hives. Key symptoms of CCD include: 1) inexplicable disappearance of the hive’s worker bees; 2) presence of the queen bee and absence of invaders; 3) presence of food stores and a capped brood.