Unpublished field trials by pesticide manufacturers show their products cause serious harm to honeybees at high levels, leading to calls from senior scientists for the companies to end the secrecy which cloaks much of their research.
The research, conducted by Syngenta and Bayer on their neonicotinoid insecticides, were submitted to the US Environmental Protection Agency and obtained by Greenpeace after a freedom of information request.
Neonicotinoids are the world’s most widely used insecticides and there is clear scientific evidence that they harm bees at the levels found in fields, though only a little to date showing the pesticides harm the overall performance of colonies. Neonicotinoids were banned from use on flowering crops in the EU in 2013, despite UK opposition.
Bees and other insects are vital for pollinating three-quarters of the world’s food crops but have been in significant decline, due to the loss of flower-rich habitats, disease and the use of pesticides.
The newly revealed studies show Syngenta’s thiamethoxam and Bayer’s clothianidin seriously harmed colonies at high doses, but did not find significant effects below concentrations of 50 parts per billion (ppb) and 40ppb respectively. Such levels can sometimes be found in fields but concentrations are usually below 10ppb.