Pesticide combination affects bees' ability to learn

March 27, 2013
A honey bee robs a comb. Photo by Lynn Ketchum

Two new studies have highlighted a negative impact on bees' ability to learn following exposure to a combination of pesticides commonly used in agriculture. The researchers found that the pesticides, used in the research at levels shown to occur in the wild, could interfere with the learning circuits in the bee's brain. They also found that bees exposed to combined pesticides were slower to learn or completely forgot important associations between floral scent and food rewards.

In the study published today (March 27, 2013) in Nature Communications, the University of Dundee's Dr Christopher Connolly and his team investigated the impact on bees' brains of two common : pesticides used on crops called neonicotinoid pesticides, and another type of pesticide, coumaphos, that is used in hives to kill the Varroa mite, a parasitic mite that attacks the .

The intact bees' brains were exposed to pesticides in the lab at levels predicted to occur following exposure in the wild and was recorded. They found that both types of pesticide target the same area of the bee brain involved in learning, causing a loss of function. If both pesticides were used in combination, the effect was greater.

The study is the first to show that these pesticides have a direct impact on pollinator brain physiology. It was prompted by the work of collaborators Dr Geraldine Wright and Dr Sally Williamson at Newcastle University who found that combinations of these same pesticides affected in bees. Their studies established that when bees had been exposed to combinations of these pesticides for 4 days, as many as 30% of honeybees failed to learn or performed poorly in memory tests. Again, the experiments mimicked levels that could be seen in the wild, this time by feeding a sugar solution mixed with appropriate levels of pesticides.

Dr Geraldine Wright said: "Pollinators perform sophisticated behaviours while foraging that require them to learn and remember floral traits associated with food. Disruption in this important function has profound implications for honeybee colony survival, because bees that cannot learn will not be able to find food."

Together the researchers expressed concerns about the use of pesticides that target the same area of the brain of insects and the potential risk of toxicity to non-target insects. Moreover, they said that exposure to different combinations of pesticides that act at this site may increase this risk.

Dr Christopher Connolly said: "Much discussion of the risks posed by the neonicotinoid insecticides has raised important questions of their suitability for use in our environment. However, little consideration has been given to the miticidal pesticides introduced directly into honeybee hives to protect the from the Varroa mite. We find that both have negative impact on honeybee brain function."

"Together, these studies highlight potential dangers to pollinators of continued exposure to pesticides that target the insect nervous system and the importance of identifying combinations of pesticides that could profoundly impact pollinator survival."

Explore further: Scientists examine how common pesticide mixes may affect bee die-offs

More information: 'Cholinergic pesticides cause mushroom body neuronal inactivation in honeybees'. Nature Communications.dx.doi.org/10.1038/ncomms2648

'Exposure to multiple cholinergic pesticides impairs olfactory learning and memory in honeybees.' J Exp Biol Advance Online Articles. 7 February 2013 as doi:10.1242/jeb.083931

Related Stories

Honeybees entomb to protect from pesticides

April 8, 2011

(PhysOrg.com) -- With the drastic rise in the disappearance of honeybee colonies throughout the world in recent years there has become a large focus on the study of honeybees and the effects of pesticides on their colonies. ...

Antibiotic dangers trap bees in a Catch 22

November 2, 2011

Honey bees are trapped in a Catch 22 where antibiotics used to protect them from bacterial illnesses ravaging hives are making them die from commonly used pesticides, some of which are used to ward-off bee-killing parasites.

Pesticides hit bumblebee reproduction

June 20, 2012

Scientists already knew that neonicotinoid pesticides, which affect insects' nervous systems, can alter bee behaviour, putting these vital pollinators, already threatened by habitat loss and disease, further at risk.

Recommended for you

Genomes uncover life's early history

August 24, 2015

A University of Manchester scientist is part of a team which has carried out one of the biggest ever analyses of genomes on life of all forms.

Rare nautilus sighted for the first time in three decades

August 25, 2015

In early August, biologist Peter Ward returned from the South Pacific with news that he encountered an old friend, one he hadn't seen in over three decades. The University of Washington professor had seen what he considers ...

Study shows female frogs susceptible to 'decoy effect'

August 28, 2015

(Phys.org)—A pair of researchers has found that female túngaras, frogs that live in parts of Mexico and Central and South America, appear to be susceptible to the "decoy effect." In their paper published in the journal ...

Why a mutant rice called Big Grain1 yields such big grains

August 24, 2015

(Phys.org)—Rice is one of the most important staple crops grown by humans—very possibly the most important in history. With 4.3 billion inhabitants, Asia is home to 60 percent of the world's population, so it's unsurprising ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

Caliban
not rated yet Mar 27, 2013
Way past time to introduce a ban of these pesticides.
Given that approximately 1/3 of food crops are polinated by bees, and the association of the poisons with CCD --and now these findings-- continued use can easily be predicted to cause major negative impact upon world food supplies.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.