Bees’ preference for insecticide-laced flowers puts them at risk

Bees prefer to take nectar laced with the world's most commonly used group of insecticides - behaviour that could have serious repercussions given they are top pollinators for food crops.

The EU has partially blocked the use of these neonicotinoid insecticides, so named because they are similar chemically to the nicotine found in tobacco.

Scientists are now speculating that honey bees and buff-tailed bumblebees are attracted to them through a similar mechanism that causes smokers to get hooked on cigarettes.

The journal Nature released two pieces of research this evening (wed) on neonicotinoid insecticides.

Both show that the bees are being exposed to higher than expected levels of the insecticides by collecting nectar and pollen from flowering crops sprayed with the chemicals.

One study also shows that this exposure leaves the bees less “fit” and unable to reproduce effectively.

This could have huge implications, given bee numbers are already in decline due to other pressures.

"Our study showed that these bees can't taste the insecticide so they can't avoid it," said Prof Jane Stout, professor of botany at Trinity College Dublin.

She co-authored one paper with lead scientist Prof Geraldine Wright of Newcastle University.

‘Seriously worrying’

“This increases their exposure and they actually seem to prefer it. This is putting them at risk of poisoning when they eat contaminated nectar.” This was “seriously worrying” given the current global pollinator decline.

The insecticides were developed during the 1990s and environmental impacts began to emerge from 2008. The EU moved to restrict the use of several neonicotinoids in 2013.

Profs Wright and Stout decided to test arguments that, given the choice, bees would prefer to forage on flowers with no insecticide.

They offered the insects a choice of sugar solution or sugar laced with a neonicotinoid. Far from avoiding it, both honeybees and bumblebees preferred the neonicotinoid solution.

They also showed that the bees could not taste the chemicals and so could not avoid them if they wished to. They also found that the bees ate less when exposed to the chemicals.

The second paper took away arguments that the artificial feeding tests would not be duplicated in the field.

Maj Rundlöf of Lund University, Sweden grew oilseed rape using seeds coated in neonicotinoid.

The resultant field saw reduced wild bee density, bumblebee colony growth and reproduction. This she said showed such insecticide use posed a “substantial risk” to wild bees in agricultural settings.

“The conclusion is there is clear evidence of the negative impact from neonicotinoids and not just to honeybees - it is much broader and affects other pollinators,” Prof Stout said.