Bumblebees’ ability to produce the buzzing – or vibration – that enables them to pollinate key commercial food crops may be harmed by the controversial pesticides neonicotinoids, according to new research.
The preliminary findings of the study – which examined a type of pollination unique to bees known as ‘buzz pollination’ – will be presented at the British Ecological Society’s annual meeting in Liverpool on 13 December.
In standard forms of pollination, bees collect pollen by simply brushing it off plants’ anthers. But buzz pollinated plants – including crops such as tomatoes, potatoes and aubergines – guard their pollen inside the anther and release it through small pores in the tip.
According to Dr Penelope Whitehorn of the University of Stirling, who led the study: “Bees produce a vibration – or buzz – to shake pollen out of the anther like a pepper pot.”
“The bee lands on a flower, curls her body around the anther and grips the base with her mandibles. She then rapidly contracts the flight muscles to produce the vibration, without beating her wings.”
Ecologists have studied buzz pollination for decades but many unanswered questions remain, such as the degree to which bees are born being able to buzz pollinate or whether it is a skill they must learn through practice.
Because buzz pollination requires a complex set of behaviours, Dr Whitehorn wanted to find out whether it was affected by neonicotinoids.
She split a bumblebee colony into three groups of workers and fed them different field-realistic doses of the neonicotinoid thiamethoxam.
She then measured how much pollen these bees collected from buffalo-bur flowers Solanum rostratum in the lab, and recorded their buzzes to analyse the acoustic properties.
The results reveal that learning is key to buzz pollination, and that the more bumblebees practice, the more pollen they collect over time. The study also showed that bumblebees fed field-relevant doses of thiamethoxam did not collect more pollen over time, suggesting the insecticide was affecting their ability to learn.
“The study adds to the now large body of evidence from lab- and field-based studies that neonicotinoids reduce learning and memory in bees, impair their communication, foraging efficiency and immune systems and, crucially, reduce their reproductive success as well as the pollination services that they can provide.
“These chemicals do have serious implications for wild bee populations in agricultural landscapes but some, notably from the agrochemical industry, still promote their use,” Dr Whitehorn warns.
In 2013, the EU issued a moratorium limiting use of three neonicotinoids on crops attractive to bees. This moratorium is still in place and is currently under review by the European Food Standard Agency, which will be concluded in early 2017.
Dr Penelope Whitehorn will present her findings at the British Ecological Society annual meeting at the ACC, Liverpool on Tuesday 13 December 2016.