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It is one of the most soothing sounds in the English countryside.

But the buzzing of bumblebees as they fly from flower to flower has been altered by pesticides, making it harder for them to collect pollen.

Monitoring the bees with microphones, British researchers found neonicotinoid pesticides affect ‘buzz pollination’ – the vibrations used by the stripy insects to explode pollen out of flowers.

Those exposed to the chemicals collected around half the amount of pollen.

The study’s lead author, Dr Penelope Whitehorn from the University of Stirling, said: ‘Our findings have implications for the effects of pesticides on bee populations as well as the pollination services they provide.

The buzzing of bumblebees as they fly from flower to flower has been altered by pesticides

The buzzing of bumblebees as they fly from flower to flower has been altered by pesticides

‘They also suggest that pesticide exposure may impair bees’ ability to perform complex behaviours, such as buzz pollination.’

Last week Environment Secretary Michael Gove backed a Europe-wide ban on neonicotinoids, which are intended to defend crops from insects like weevils and aphids, but also harm bees’ ability to forage for food and reproduce.

A study in October found three-quarters of honey samples from every continent except Antarctica were laced with at least one of these pesticides – which act as nerve agents.

The latest research studied captive colonies of bumblebees visiting buzz-pollinated flowers, monitoring their behaviour.

Scientists analysed the acoustic signal produced during buzz pollination to detect changes in buzzing behaviour through time.

They found long-term exposure to neonicotinoid pesticide, at similar levels to those found in agricultural fields, interfered with the vibrations of the bees.

Dr Whitehorn said: ‘We found that control bees, which were not exposed to the pesticide, improved their pollen collection as they gained experience, which we interpreted as an ability to learn to buzz pollinate better.

Some bees which were exposed to the chemicals had collected around half the amount of pollen

Some bees which were exposed to the chemicals had collected around half the amount of pollen

Some bees which were exposed to the chemicals had collected around half the amount of pollen

‘However, bees that came into contact with pesticide did not collect more pollen as they gained more experience, and by the end of the experiment collected between 47 per cent and 56 per cent less pollen compared to the control bees.’

Bumblebees usually feed through gathering pollen on their hairy bodies or using their tongues, with short-tongued insects feeding on flowers with short nectar tubes, and long-tongued bees having evolved to choose different plants.

Buzz pollination is needed when these strategies fail, in plants like blueberry, cranberry and Senna flowers which have evolved to keep a tighter hold on their tightly-packed pollen.

In this case, bumblebees contract their flight muscles, which produces strong vibrations, resulting in an explosion of pollen which can be collected from their fur and deposited into the pollen baskets on their hind legs.

The researchers want to explore whether pesticides affect the memory and cognitive ability of bumblebees, which are important in complex behaviours like this type of pollination.

Responding to the study published in the journal Scientific Reports, Friends of the Earth’s Sandra Bell said: ‘This study adds to the overwhelming stack of evidence that neonicotinoid pesticides harm bees – this time showing that these chemicals could hamper bumblebee’s ability to pollinate some of our favourite fruits by buzz pollination.

‘Farmers across the UK are already successfully farming without neonics – the government and NFU must do far more to help farmers to produce the food we all need without bee-harming chemicals.’ 



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