An international panel of scientists is calling for an evidence-driven debate over whether neonictinoids are to blame for declines in bees and other insect pollinators.
An EU ban on certain neonicotinoid insecticides was introduced in December 2013 because of fears they are harming pollinating insects.
A restatement of the scientific evidence on neonicotinoids has been published in Proceedings of the Royal Society B.
The restatement, from a group of nine scientists led by Professor Charles Godfray and Professor Angela McLean of the Oxford Martin School at Oxford University, clarifies the scientific evidence available on neonicotinoids, to enable different stakeholders to develop coherent policy and practice recommendations.
Defra secretary of state Owen Paterson told HW: "There's not any field evidence justifying a ban."
He said Defra's pollinator strategy shows Defra is taking the issue seriously: "It's massively important but we didn't want to see knee jerk reactions. Banning modern products developed recently means sadly farmers may now fall back on older products that are not good for the environment. We want more field trials across Europe."
Paterson said other EU states formed a "very significant campaign" to ban neonicotinoids but the UK "must be steady under fire and hold more field trials."
Professor Charles Godfray said: "Pollinators are clearly exposed to neonicotinoid insecticides, but seldom to lethal doses, and we need a better understanding of the consequences of realistic sub-lethal doses to the insect individual, bee colony and pollinator population."
Professor Angela McLean added: "A major question to be addressed is what farmers will do now that they face restrictions on the use of neonicotinoids. Will they switch to crops that need less insecticide treatment or might they apply older but more dangerous chemicals?"
The restatement describes how much insecticide is present in a treated plant and how much is consumed by pollinators. It goes on to summarise how neonicotinoids affect individual bees and other pollinators, and the consequences at the colony and population levels.
In reaction to this study, Professor Ian Boyd, chief scientific advisor at Defra, said: "It is essential that policies on the use of pesticides are built on sound scientific evidence. This paper provides an independent assessment of this subject, which will provide clarity and authority in order to help people make more informed choices."
Paul de Zylva, from Friends of the Earth, commented: "This project is an important step toward much needed public and scientific debate and scrutiny. The Government should support and fund both more open science and safer ways to grow crops as part of its National Pollinator Strategy due in July."
- Since their introduction in the 1990s, the use of neonicotinoids has expanded so that today they comprise about 30% by value of the global insecticide market.
- Insects are important for pollinating many UK crops, including strawberry, raspberry, apple, pear, plum, tomato and many vegetables.
- The populations of both managed honeybees and wild pollinators were declining before the widespread use of neonicotinoids, with habitat change and honeybee disease thought to be particularly important causes.
- A series of experiments have raised the possibility that widespread neonicotinoid use may exacerbate pollinator decline, though other studies find fewer effects of the insecticide.