30 March 2012

Decline In Honeybees Linked To Pesticides

It has been shown for the first time that common crop pesticides seriously harm bees by damaging their renowned ability to navigate home.

Honeybees are essential to food supplies as they pollinate a third of the food we eat but the new research strongly links the pesticides to the serious decline in their numbers in the US and UK – a drop of around 50% in the last 25 years.

Scientists found that bees consuming one pesticide suffered an 85% loss in the number of queens their nests produced, while another study showed a doubling in "disappeared" bees – those that failed to return from food foraging trips. The significance of the new work, published in Science, is that it is the first carried out in realistic, open-air conditions.

Prof David Goulson, at the University of Stirling and leader of one of the research teams said: "People had found pretty trivial effects in lab and greenhouse experiments, but we have shown they can translate into really big effects in the field. This has transformed our understanding.

"If it's only one metre from where they forage in a lab to their nest, even an unwell bee can manage that."

Prof Mickaël Henry, at INRA in Avignon, France, who led a separate research team, said: "Under the effects we saw from the pesticides, the population size would decline disastrously, and make them even more sensitive to parasites or a lack of food."

Nobody has been able to show for certain the exact cause for the decline in honeybee numbers but pesticides, the varroa mite and other parasites, and destruction of the flower-rich habitats are thought to be the key reasons.

One particular class of chemicals, neonicotinoids, have been suspended from use in Germany, Italy and France but the pesticide manufacturers and the UK government deny it cause significant problems for bees.

"The UK has a robust system for assessing risks from pesticides and all the evidence shows neonicotinoids do not pose an unacceptable risk to honeybees when products are used correctly,” A spokesperson from Department for Environment, Food and Rural Affairs (Defra) said.

Saying the new research did not change the government's position he added. “However, we will not hesitate to act if presented with any new evidence."

Julian Little, spokesman for Bayer Cropscience, criticised Prof Goulson's study: "All studies looking at the interaction of bees and pesticides must be done in a full field situation," he said. "This study does not demonstrate that current agricultural practices damage bee colonies."

Both Bayer and Defra suggested other field studies had shown no harmful effects to bees. Goulson said: "If they have done these studies, where are they? They are not in the public domain and therefore cannot be scrutinised. That raises the question of just how good they are."

(H)