(Bloomberg) -- Bayer AG and Syngenta AG face renewed pressure over their neonicotinoid farm pesticides after research funded by the companies supported accusations that the chemicals are responsible for harming bee colonies.
The study was published in the peer-reviewed journal Science at a time when the European Union’s executive arm is preparing to propose a ban on use of such pesticides in the countryside of the 28-nation trade bloc.
Bee colony numbers tested in Hungary fell 24 percent by the spring and survival of colonies in the U.K. was "generally very low" after exposure to winter oilseed rape crops treated with Bayer CropScience’s neonicotinoid clothianidin or Syngenta’s thiamethoxam pesticides, the Centre for Ecology & Hydrology, author of the study, said in a statement.
While no harmful effect was found on overwintering bees in Germany, lower reproductive success was linked to increasing levels of neonicotinoid residues in nests of wild bee species across all three countries tested.
“The neonicotinoids investigated caused a reduced capacity for all three bee species to establish new populations in the following year, at least in the U.K. and Hungary,” lead researcher Ben Woodcock said.
The results are critical to the future use of such chemicals in Europe. Bayer and Syngenta clashed with the EU in court earlier this year over temporary bans on the products. The European Commission has drafted proposals to largely outlaw their use outside of greenhouses. While it hasn’t yet formally put forward the curbs, the commission sent draft regulations to the European Parliament in March.
"This major study marks a watershed moment in the fight to protect our bees," Greenpeace UK’s chief scientist Doug Parr said in a statement. "The case for a permanent ban on these pesticides is now unassailable."
While the latest study demonstrated negative effects from the chemicals, they can be used for good, according to Woodcock. The ability to protect whole plants with low dosages curbs the need for spraying broad spectrum insecticides and allows control of pests resistant to other controls.
"There may be opportunities to mitigate negative impacts of neonicotinoid exposure on bees through improved honeybee husbandry or availability of flowering plants for bees to feed on," he said.
Good beekeeping practices and planting wild flower margins could mean that the impact of neonicotinoids "can be minimal or in some cases even positive," Syngenta said in a statement. Bayer pointed to inconsistent results in different countries, adding that colony deaths in the U.K. were too high to support scientifically robust conclusions.
"Bayer remains convinced that neonicotinoid seed treatments for oilseed rape have no short- or long-term negative effects on bees and that these seed treatments are a useful and effective tool for farmers," it said.