Imidacloprid effects on bees
No single factor is responsible for the malady, however
In January 2013, the
Imidacloprid was first registered in the United Kingdom in 1993 and in the United States and France in 1994. In the mid to late 1990s, French beekeepers reported a significant loss of bees, which they attributed to the use of imidacloprid. In 1999, the French Minister of Agriculture suspended the use of imidacloprid on sunflower seeds and appointed a team of expert scientists to examine the impact of imidacloprid on bees. In 2003, this panel, referred to as the Comité Scientifique et Technique (CST, or Scientific and Technical Committee) issued a 108-page report, which concluded that imidacloprid poses a significant risk to bees. In 2004, the French Minister of Agriculture suspended the use of imidacloprid as a seed treatment for maize (corn). Despite these bans, colony collapse disorder still is occurring.
Like most insecticides, imidacloprid is highly toxic to bees, with a contact acute LD50 = 0.078 μg a.i./bee and an acute oral LD50 = 0.0039 μg a.i./bee. Imidacloprid was first widely used in the United States in 1996 as it replaced 3 broad classes of insecticides. In 2006, U.S. commercial migratory beekeepers reported sharp declines in their
In a British parliamentary inquiry in 2012, the Environmental Audit Committee accused European regulators of ignoring evidence of imidacloprid risk to bees. The committee said that imidacloprid data available in the regulators' own assessment report shows "unequivocally that imidacloprid breaks down very slowly in soil, so that concentrations increase significantly year after year with repeated use, accumulating to concentrations very likely to cause mass mortality in most soil-dwelling animal life." The committee submitted a lengthy list of failings in current regulations including concerns that current regulations were set up for pesticide sprays, not systemic chemicals like imidacloprid that is used to treat seeds. They also expressed concern that only effects on honeybees have been considered despite the fact that 90% of pollination is carried out by different species, such as
Researchers from the
In May 2012, researchers at the University of San Diego released a study that showed that honey bees treated with a small dose of imidacloprid, comparable to what they would receive in nectar and formerly considered a safe amount, became "picky eaters," refusing nectars of lower sweetness and preferring to feed only on sweeter nectar. It was also found that bees exposed to imidacloprid performed the "waggle dance," the movements that bees use to inform hive mates of the location of foraging plants, at a lesser rate.
Also in 2012, USDA researcher Jeff Pettis published the results of his study, which showed that bees treated with sub-lethal or low levels of imidacloprid had higher rates of infection with the pathogen