Dramatic decline of bees caused by modern pesticides damaging their ability to home in on their hives, say researchers

Dramatic decline of bees caused by modern pesticides damaging their ability to home in on their hives, say researchers - Finding comes after 650 honeybees were 'tagged' - Pesticides introduced in the 1990s are to blame - Bees are in dramatic decline, and scientists believe the answer may be in their homing instinct.

They have found the latest generation of pesticides is stopping the foragers finding their way back to the hive.

French researchers tagged 650 honeybees with tiny microchips attached to their necks which tracked all their movements.

Homing in on the answer: Researchers say pesticides are preventing bees from finding their way back to the hive

Half the bees were exposed to low doses of insecticide similar to what they would find in the wild, and when released, these ones were found to be two or three times more likely to die away from their hive.

Meanwhile British researchers, who have been working on bumblebees at Stirling University in Scotland found that when growing colonies were exposed to these chemicals, they were smaller than those not treated.

After six weeks the bumblebees - exposed to the same type of pesticide called a neo-nicotinoid - were up to 12 per cent smaller as it appeared less food was coming back to the nest.

Of even more concern to the Scottish scientists was that the number of new Queens – which go out and find new nests after winter – decreased by 85 per cent, which suggests a huge decrease in the number of new nests.

Neo-nicotoinoids, based on the chemical nicotine, were introduced as an insecticide in the 1990s, and have become the most popular for crops and gardens in the world.

Although bumblebees were already in decline, their numbers have fallen faster and honeybee populations are thought to have halved since the 1980s in Britain.

Both types of bees live in colonies where some of the inhabitants are foragers who travel up to a mile a day looking for new plants and bringing food back. Their lifespan can be just a week.

Mikael Henry of the National Institute of Agricultural Research in Avignon, France, said the chemicals seem to be attacking the bees’ navigation abilities, and if it continues at this rate, many colonies will not recover.

While pesticides are tested to make sure they do not kill bees - he believes they may be wiping them out indirectly.

He said: ‘Our study raises important issues regarding pesticide authorisation procedures.

Common practice: Farmers routinely use insecticides to protect their crops from pests

‘So far, they mostly require manufacturers to ensure that doses encountered on the field do not kill bees, but they basically ignore the consequences of doses that do not kill them but may cause behavioural difficulties.’

Dr Dave Goulson, who worked on the Scottish study, also published in the journal Science, said: ‘We have seen big changes in the bees’ size and in particular in the number of queens, which is remarkable.

‘Putting these studies together, it suggests the answer may be the navigation abilities are being affected by base levels of neonicotinoid pesticides and this is having a substantial population impact.

‘Bumblebees pollinate many of our crops and wild flowers. The use of these pesticides on flowering crops poses a threat to their health and urgently needs to be re-evaluated.’

Neonicotinoids are applied to the seeds of plants rather than the plant itself which was thought to be more environmentally friendly.

They contain compounds which are thought to interfere with the bees central nervous system, and is having an impact on their memory and learning including finding their way back home - even from a short distance away.

The British Beekeepers Association advocates trying to improve rather than ban these pesticides, as new ones may prove to be even worse for bees. ( dailymail.co.uk )