The Crop Protection Association has warned further research is needed to establish the cause of a 76 per cent drop in flying insect numbers in Germany.
The massive decline was recorded by a study published in scientific journal Plos One, which built on the work of amateur entomologists.
All kinds of flying insects, including wasps and flies, had been collected for 27 years at 63 nature reserves across the country.
Looking at the average weight of the insect samples, researchers found a huge drop of 76 per cent since 1989, as well as a mid-summer decline of 82 per cent.
Changes to habitat type, land use and weather could not explain the drop-off in numbers, leading some of the scientists who carried out the study to speculate about pesticides contributing to the problem.
Professor Dave Goulson, who co-authored the paper, said: “Farmland has very little to offer for any wild creature, but exactly what is causing their death is open to debate.
“It could simply be there is no food for them, or it could be exposure to chemical pesticides, or a combination of the two.”
A previous paper Prof Goulson worked on suggested farmland birds were being killed by neonicotinoids, a claim hotly disputed by the NFU.
Crop Protection Association chief executive Sarah Mukherjee said: “While these findings are clearly concerning and further research is needed to establish whether these declines are more widespread, we should not rush to blame the nearest chemical.
“The causes of these issues are complex and multifactorial and include issues such as habitat loss, availability of food and agricultural practices.
“We believe productive farming can exist hand-in-hand with the promotion of biodiversity, and there are a number of organisations, such as LEAF and Conservation Grade which demonstrate this reality.
“Some of the best examples of conservation farming in the UK take a conventional approach which includes pesticides, and by maximising yields from land already under cultivation, more wild spaces are preserved for biodiversity.”