Exposure to common air pollutants found in diesel exhaust pollution can affect the ability of honeybees to recognise floral odours, according to researchers form University of Southampton.

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Honeybees use floral odours to help locate, identify and recognise the flowers from which they forage.

The Southampton team, led by Dr Tracey Newman and Professor Guy Poppy, found that diesel exhaust fumes change the profile of flora odour. They say that these changes may affect honeybees' foraging efficiency and, ultimately, could affect their ability to pollinate crops, with implications for growers.

The study mixed eight chemicals found in the odour of oilseed rape flowers with clean air and with air containing diesel exhaust fumes. Six of the eight chemicals reduced (in volume) when mixed with the diesel exhaust air and two of them disappeared completely within a minute, meaning the profile of the chemical mix had completely changed. The odour mixed with the clean air was unaffected.

The researchers had the same result when they mixed flower odours with NOx gases (nitric oxide and nitrogen dioxide), also found in diesel exhaust. They believe these gasses play a key role in altering plants' odours. Honeybees 'shown' the altered plant odour could no longer recognise it as coming from a crop on which they feed.

Dr Newman, a neuroscientist and study leader commented, "Honeybees have a sensitive sense of smell and an exceptional ability to learn and memorize new odours. NOx gases represent some of the most reactive gases produced from diesel combustion and other fossil fuels, but the emissions limits for nitrogen dioxide are regularly exceeded, especially in urban areas.

"Our results suggest that that diesel exhaust pollution alters the components of a synthetic floral odour blend, which affects the honeybee's recognition of the odour. This could have serious detrimental effects on the number of honeybee colonies and pollination activity."

Due to the pollination'services' the bees provide, as well as the production of honey, honeybees are estimated to be worth £430 million a year to the UK alone. "However to forage effectively they need to be able to learn and recognize the plants," said Ecologist and co-author Professor Poppy. "The results indicate that NOx gases – particularly nitrogen dioxide – may be capable of disrupting the odour recognition process that honeybees rely on for locating floral food resources."