A widely used insecticide, the neonicotinoid imidacloprid, “does not significantly harm honey bee colonies at real-world doses,” contrary to concerns that neonics, as they are called, are to blame for population declines, says a University of Maryland study. Over a three-year period, researchers examined the impact of imidacloprid on honeybees. They had to expose the bees to at least four times the normal application of the insecticide before there was a sharp drop in winter survival rates. At 20 times the normal rate of exposure, the colonies displayed more severe consequences. The lead author of the study, Galen Dively, said the neonic “is not the sole cause. It contributes, but there is a bigger picture.”
Climate stress, malnutrition, and exposure to multiple pesticides also could be factors in the winter die-offs of colonies, said researchers. At the highest doses used in the study, colonies became more susceptible to Varroa mites, also tagged as a prime suspect. Dively said honeybee losses were “a multi-factorial issue, with lots of stress factors. Honeybees have a lot of pests and diseases to deal with.” Insecticides are one factor, “not the lone villain,” he said.
Groups such as Greenpeace are campaigning for the EPA to ban neonics. The European Union imposed a two-year ban on imidacloprid and two other neonics in 2013 in response to a collapse in honeybee numbers worldwide.
The debate has taken on ideological dimensions, “with some environmentalists fearing they [neonicotinoids] could wipe out bees entirely, while agrichemical companies say their responsible use is harmless and stoke fears about food security and the inability to feed a growing world population without them,” says the Guardian. It quotes a biologist as saying most scientists agree that loss of habitat is the greatest factor, with disease and pesticides as contributing factors.