Pollinating insects are coming under greater threat around the world due to expanding use of chemicals, climate change and other factors.
Neonicotinoids are used commonly on crops in Europe while coumaphos are used widely in the United States.
Two separate U.K. studies have now found that both the insecticides cause neurological damage to the pollinators in the laboratory.
The European Commission recently called for a temporary moratorium on the use of neonicotinoids after a report by the European Food Safety Authority warned that they posed an acute risk to pollinating insects.
But Bayer Crop Science Limited, which produces some of the pesticides, questions the findings.
It says the U.K. researchers applied the chemicals directly to the insects, rather than observing their effects in the field.
Photo: Jeff Pettis - Agricultural Research Service