WHAT would happen to the vital role bumblebees play in our lives if they stopped buzzing? That is a question scientists at Stirling University think they have answered – and it’s not good news for bees or for those people whose jobs depend on them being able to pollinate.
When a bumblebee collects pollen, it often does so by buzzing against a plant to release pollen through vibrations.
The bee can then collect the pollen and go about its important work of pollination, on which some 80 per cent of plant species depend for their existence. However, a study by the researchers at the university has shown categorically that pesticides significantly reduce the number of pollen grains a bumblebee is able to collect.
This has long been a controversial subject with pesticide manufacturers and users saying they do not affect bees, while evidence has mounted that this is not the case. The Stirling study shows for the first time that pesticides have a measurable effect on bees and that damage harms the pollination process.
The ground-breaking research, conducted by a team from the Faculty of Natural Sciences, found that field-realistic doses of neonicotinoid pesticide – the world’s most common insecticide – affects the behaviour of bees, ultimately interfering with the type of vibrations they produce while collecting pollen. Research fellow Dr Penelope Whitehorn, who led the study, said: “Our result is the first to demonstrate quantitative changes in the type of buzzes produced by bees exposed to field-realistic levels of neonicotinoid.
“We also show that buzz pollinating bees exposed to the pesticide collect fewer pollen grains.”
Whitehorn, working with associate professor Dr Mario Vallejo-Marin, looked at a complex type of pollination, called buzz pollination, in which bees use vibrations to remove pollen from flowers. They studied captive colonies of bumblebees visiting buzz-pollinated flowers, monitoring their behaviour and collecting bee buzzes using microphones.
The scientists then analysed the acoustic signal produced during buzz pollination to detect changes in buzzing behaviour through time.
They found that chronic exposure to the pesticide, at similar levels to those found in agricultural fields, interfered with the vibrations of the bees as they collected pollen which, in turn, reduced the amount of pollen collected.
Dr Whitehorn explained: “We found that control bees, who 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.
“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 control bees.”
The study is likely to be controversial. It follows two research projects that were published during the summer after studies in Canada and across Europe which suggested that widely used pesticides affected both honeybee colonies and wild bees. Both studies were attacked by proponents of pesticides.
The Stirling study provides further evidence that pesticides do damage the ability of bees to pollinate due to the reduction in their buzzing capabilities, with manufacturers and farmers yet to respond to this latest research.
Vallejo-Marin said: “Our findings have implications for the effects of pesticides on bee populations as well as the pollination services they provide.
“They also suggest that pesticide exposure may impair bees’ ability to perform complex behaviours, such as buzz pollination.
“The next step in this research would be to establish the mechanism by which the pesticide is affecting the bees. We think pesticides may be affecting the memory and cognitive ability of bumblebees, which may be very important when conducting complex behaviours.”
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