Butterflies have joined the ranks of honeybees, bumblebees, moths and other insects that may be feeling the effects of the controversial neonicitinoid insecticides.
UK researchers have found that even insects which do not pollinate oilseed rape may be harmed by the chemicals.
The National Farmers' Union bee health specialist said there had been "no game-changing body of evidence to settle the debate".
Neonicotinoids - or neonics for short - are insecticides similar to nicotine, acting on the central nervous system to paralyse insects.
One of them, imidacloprid, is the most widely used insecticide in the world.
Neonicotinoid pesticides were banned from use on flowering crops by the EU in 2013, a move opposed by the UK government.
Ministers granted a temporary lifting of the ban in 2015 after the NFU argued it was needed to fight the cabbage stem flea beetle.
In May this year, farming minister George Eustice rejected an NFU call to allow the pesticide to be used on some oilseed rape crops.
An American study found that butterfly species in California's Central Valley have dipped since the 1990s - around the same time that neonicotinoids were introduced.
Matthew Forister of the University of Nevada and his colleagues report in Biology Letters that those two events may be linked.
They ruled out warmer summers or other possible causes, and found that butterfly species in areas with higher pesticide use experienced the steepest declines.
A team from the Centre for Ecology & Hydrology studied the fate of 62 wild bee species over 18 years - the period since the widespread use of neonicitinoids began.
They found a link between the use of the pesticides and the odds of a particular bee population going extinct, they report in the journal Nature Communications.
The decline was, on average, three times stronger among species that regularly feed on the crop such as buff-tailed bumblebee (Bombus terrestris) compared to species that forage more widely.
The scientists report that they found evidence suggesting that neonicotinoid use is linked to large-scale and long-term decline in wild bees. But lead author Dr Ben Woodcock said: "Although we find evidence to show that neonicotinoid use is a contributory factor leading to wild bee species population decline, it is unlikely that they are acting in isolation of other environmental pressures.
"Wild bees have undergone global declines that have been linked to habitat loss and fragmentation, pathogens, climate change and other insecticides."
The NFU's bee health specialist, Dr Chris Hartfield, said: "Since the restrictions on neonicotinoids began in 2013 there has been no game-changing body of evidence to settle the debate."
"The Centre for Ecology and Hydrology study is another interesting piece to an unsolved puzzle about how neonicotinoid seed treatments affect bees. It does not show that neonicotinoids are causing widespread declines in pollinator populations and it certainly does not show that neonicotinoid use has caused any extinction of bees in England."
"Bees provide valued agricultural pollination which is essential in food production. Farmers have increased their planting of pollen and nectar mix - food for bees - by 134% in the past two years. Over 7,000 acres of seed mixes for bees have been voluntarily planted by farmers to enhance land lying fallow. It is not in any farmers' interests to harm bees."
"The NFU remains committed to lobbying for science-based regulation across the board."
You can read the original article from the Plymouth Herald HERE