Pesticides which have been linked with the decline in bees could also harm other wildlife such as butterflies, mice and partridges, it has emerged.

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Many believe that bee numbers are falling because of pesticides
Seeds treated with the 'neonicotinoid' pesticides could kill birds or mice, a study in the Journal of Applied Ecology from the British Ecological Society has suggested.

Professor Dave Goulson, the author of the study, said: "Any pesticide that can persist for many years, build up in soil and leech into waterways is likely to have effects far beyond the pest insects it intends to target."

The European Union has banned using three of types of the pesticide on flowering crops, which are attractive to bees, for two years but they are still being used on other crops such as cereals.

Neonicotinoids are intended to affect insects by attacking their nervous systems, causing paralysis and eventually death, but less than 10 per cent of the active ingredient soaks in to plant seeds.

The rest, if used regularly, can accumulate in soil to concentration levels higher than those required to kill insects such as bees in soil, damaging soil health and killing non-target invertebrates underground.

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Campaigners have worked hard to pressure the EU into temporarily banning three nicotinoids
Prof Goulson argues that the ban is not enough, saying: "Any pesticide that can persist for many years, build up in soil and leach into waterways is likely to have effects far beyond the pest insects it intends to target."

"This is particularly so when the pesticide is highly toxic to non-target organisms. For example, less than one part per billion of the neonicotinoid imidacloropid in streams is enough to kill mayflies."

He asserted that the threat to other wildlife may not be effectively dealt with by the EU's partial ban, as the length of time is not long enough to get the neonicotinoids out of animal, bird and insect habitats.

He also said: "Neonicotinoids will still be widely used on cereals, so the broader environmental impacts are likely to continue."

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Beekeepers have had to work hard to keep their bees alive over the long, harsh winter
Bees are under threat in the UK and populations have also suffered due to a poor summer and the prolonged, cold winter made it hard for bees to forage for pollen and nectar.

More than a third of beehives across the country were lost in the worst winter for bees since records began six years ago. In south west England, over half of beehives were lost.

Last year's honey crop was down by 70 per cent, and Tim Lovett of the British Beekeepers' Association has described the losses of bees as "more dramatic than foot-and-mouth was on the national beef herd".

However Professor John Pickett, head of the Department for Biological Chemistry, Rothamsted Research, played down the effect of neonicotinoid pesticides, saying: "All commercial pesticides are tested scrupulously and with immense rigour for non-target effects and have to be used in a manner that means they cannot have important effects on the environment.

"If you test pesticides out of context you are likely to find all kinds of effects but that is not necessarily indicative of a wider effect and strict registration rules exist that are aimed at protecting the environment."