A common pesticide could be making honeybees dim-witted and affecting their survival by impairing their ability to find nectar-producing flowers, University of Otago research has found.
The researchers, led by Dr Elodie Urlacher, put bees in miniature metal harnesses in the lab and found those that had been exposed to minute amounts of a pesticide called chlorpyrifos were significantly worse at remembering and learning new odours.
The research added to a body of research on the effect pesticides had on bees, which included memory loss and links to colony collapse, but was the first to specifically link chlorpyrifos to memory and learning deficits and to determine the dosage at which bees were impaired, Dr Urlacher said.
Other research had shown links between chlorpyrifos and bees having motor deficits.
The Otago University findings were important because one of the ways bees knew what flowers were producing nectar at different times was through remembering the odour they produced, she said.
Not being able to remember odours - which bees are normally extraordinarily good at - could threaten their survival and limit their ability to pollinate crops that were important food sources for humans.
It was also of concern because chlorpyrifos, which is used worldwide to protect food crops against insects, could travel great distances from where it was sprayed and trace elements had even been found at both poles.
"Our findings raise some challenging questions about regulating this pesticide's use.
"It's now clear that it is not just the lethal effects on bees that need to be taken into account, but also the serious sub-lethal ones at minute doses,'' Dr Urlacher said.
In their study, researchers from the zoology and chemistry departments collected bees from 51 hives across 17 locations in Otago and measured their chlorpyrifos levels.
They detected low levels of the pesticide in bees at three of the 17 sites and in six of the 51 hives they examined.
In the lab they fed other bees - which they cooled down using ice to stop them moving and then put in small harnesses - with similar amounts of the pesticide and put them through learning performance tests.
The ones who had been fed the pesticide struggled to learn and remember which odours were connected with getting a sugar-water reward.
They poked their tongues out expecting a reward when confronted with a range of odours rather than just the odour connected with the reward.
The study identified the threshold at which chlorpyrifos began to have an effect on odour-learning and recall as 50 trillionths of a gram of chlorpyrifos ingested per bee - which is considered to be a "safe'' level.
The study was the first to establish the threshold at which a pesticide had an effect on memory specificity in bees while also measuring doses in bee populations in the field.
The research, which appeared in the Journal of Chemical Ecology, was supported by the Marsden Fund of New Zealand.
