Recent research

Pesticide combination affects bees’ ability to learn

Studies have highlighted an impact on bees’ ability to learn following exposure to a combination of pesticides commonly used in agriculture. Dr Christopher Connolly (University of Dundee, UK) and his team investigated the impact of two common pesticides: neonicotinoid used on crops, and coumaphos used in honey bee colonies to kill the Varroa mite.

Intact bees’ brains were exposed to pesticides in the laboratory at levels predicted to occur following exposure in the wild, and brain activity 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 Dr Geraldine Wright and Dr Sally Williamson at Newcastle University (UK) who found that combinations of these same pesticides affected learning and memory in bees. Their studies established that when honey bees had been exposed to combinations of these pesticides for 4 days, as many as 30% 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 Wright said: “Pollinators perform sophisticated behaviour while foraging that requires them to learn and remember floral traits associated with food. Disruption in this important function has profound implications for honey bee colony survival, because bees that cannot learn will not be able to find food.”

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 Connolly said: “Much discussion of the risks posed by the neonicotinoids 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 hives to protect the bees from Varroa. We find that both have negative impact on honey bee brain function. 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”.

This research is part of the Insect Pollinators Initiative, joint-funded by the Biotechnology and Biological Sciences Research Council (BBSRC), DEFRA , the Natural Environment Research Council, the Scottish Government and the Wellcome Trust under the auspices of the Living with Environmental Change partnership.

Rob Dawson, Head of News, BBSRC, Swindon, UK

Cholinergic pesticides cause mushroom body neuronal inactivation in honey bees. Nature Communications. From 27 March 2013 at: http://dx.doi.org/10.1038/ncomms2648

Exposure to multiple cholinergic pesticides impairs olfactory learning and memory in honeybees. J Exp Biol Advance Online Articles. From 7 February 2013 at http://jeb.biologists.org/lookup/doi/10.1242/jeb.083931

Synergistic effects of non-Apis bees and honey bees for pollination services

Research published in the Proceedings of the Royal Society shows that when wild bees forage together with honey bees in almonds, the behaviour of honey bees changes, resulting in the pollination effectiveness of a single honey bee being greater than in orchards where non-Apis bees were absent. Fifty species of wild bees were identified in the study including bumble bees, small carpenter bees, sweat bees, digger bees, mining bees and blue orchard bees. “These findings highlight the importance of conserving pollinators and the natural habitats they rely on”, said lead author Claire Brittain.

With increasing global demand for pollination-dependent crops, and continued challenges that limit the supply of honey bees, such strategies to increase pollination efficiency offer exciting potential for more sustainable pollination in the future.

“We plan to investigate the mechanism behind the increased effectiveness of honey bees when other bees are present,” Brittain said. “We are also going to be looking at how to enhance floral resources for wild bees in almond orchards. We now know that honey bees move more between orchard rows when non-Apis bees are around and we need to study the reason why they move: one investigation will look at the chemical footprints that the bees are leaving on the flowers”.

Kathy Keatley Garvey, Communications Specialist, UC Davis Department of Entomology

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