Study points to widespread insecticide damage to bees

Pesticide makers question research results despite funding largest ever field trial

The world’s largest-ever field trial has shown for the first time the scale of damage to honey bees and wild bees - including the bumble bee - caused by widely-used insecticides.

The farm-based research on pesticides classified as neonicotinoids, along with a second new study in Canada, also suggests widespread contamination of landscapes and a toxic “cocktail effect” from multiple pesticides.

The landmark work provides the most important evidence yet for regulators around the world considering action against neonicotinoids, including in the EU where a total ban may be implemented this autumn.

The insecticides are currently banned on flowering crops in EU countries, including Ireland.


The negative impacts found varied across different countries, leading pesticide manufacturers to question the results of the research, which they funded and which is published in the leading journal Science.

Differences in detrimental impact may be attributable to diet.

Neonicotinoids represent a quarter of the multi-billion-dollar pesticide market but have been repeatedly linked to serious harm in bees in lab-based studies.

Bees and other pollinators are vital to food production but are in decline, in part due to loss of habitats and disease.

However, there had been few realistic field studies to date to address the role of the insecticides and only occasional evidence for colony-level harm in wild bees.

Botanist Prof Jane Stout of Trinity College School of Natural Sciences said: "This is the study we have all be waiting for." It confirms what was shown up in laboratory settings, she added.

There was criticism from industry in the past that negative effects were arising from “unrealistic doses in the lab”.

Ireland was not one of the featured countries, but the findings have direct relevance here, she said, especially as negative impacts were shown in the honeybee and in solitary wild bees including the bumble bee.

Although Ireland does not have the same scale of insecticide-dependent crops as the countries featured in the main study, Irish farmers grow some oilseed rape and there are significant winter cereal crops grown here that involve coating of seeds with pesticide.

The research took place at 33 large farmland sites spread across the United Kingdom, Germany and Hungary. "We showed significant negative effects at critical life cycle stages," said Prof Richard Pywell, from the UK's Centre for Ecology and Hydrology, and part of the research team.

“If the bees are foraging a lot on oil seed rape, they are clearly at risk. This is a large and important piece of evidence, but it is not the only evidence regulators will look at.”

The €3million cost of the research was met by Syngenta and Bayer, the companies that sell the two neonicotinoids tested, as part of a voluntary commitment to increase the available field data. But the companies were not involved in the designing, conducting or reporting of the study.

Friends of the Earth nature campaigner Sandra Bell said: “This crucial study confirms that neonicotinoid pesticides come with a nasty sting in the tail for our under-pressure bees. It’s time for a complete and permanent ban on these chemicals.”

Prof Stout said she favoured a ban on these pesticides but a new risk might arise from use of other chemicals. The use of less chemicals in farming was her preference. This would require “a shift in the way we do farming” to keep it profitable and to ensure farmers can get the yields they expect.

Irish agricultural research body Teagasc last week issued guidelines to farmers underlining the critical importance of bees in the foodchain and the role of wildflowers in facilitating thriving populations.

Addressing tillage farmers at an open day in Oakpark, Carlow, Teagasc countryside management specialist Catherine Keena, said: “Pollinators, especially bees, are important, but unfortunately are in decline. We need more wildflowers in the countryside. Bees need food all year round, requiring a diversity of flowering plants in the landscape.

She added: “Farmers can help bees by allowing space for wildflowers to grow and flower within hedgerows and field margins, around farmyards, along farm roadways and in field corners. The quest for neatness on farms should not override consideration for bees.”

Federation of Irish Beekeepers’ Associations president Gerry Ryan added: “Many beekeepers work closely with farmers placing their beehives in fields of oilseed rape, peas and beans to improve pollination of the crops. It is important for tillage farmers growing these crops to provide pollinators with wildflowers outside the main crop flowering period.

Dr Úna Fitzpatrick, chair of the All-Ireland Pollinator Plan Steering Group, said: “Ireland has 98 different species of bees and one third of them are threatened with extinction. By having more wildflowers we can help protect bees and the livelihood of farmers and growers who rely on their ‘free’ pollinator service.”

Tillage farmers were also reminded to spray crop protection products in the early morning and late evening when honey bees are less active, and to notify local beekeepers in advance of carrying out the operation.

Additional reporting: The Guardian

Kevin O'Sullivan

Kevin O'Sullivan

Kevin O'Sullivan is Environment and Science Editor and former editor of The Irish Times