July 11th, 2017
A new study, part-funded by pesticide manufacturers Bayer and Syngenta, has found that pesticides pose a major risk to European honeybees and wild bees.
The study is based on work by researchers from the Centre for Ecology and Hydrology (CEH) who carried out a large-scale experiment to assess the impact of neonicotinoid pesticides on honeybees and wild bees across Europe.
Bee populations have been declining in Europe since the 1980s. Today, over nine per cent of bee species in EU member states are considered threatened with extinction.
The experiment was carried out in the UK, Germany and Hungary and exposed three bee species to winter oilseed rape crops treated with either neonicotinoid clothianidin pesticides (NCP) from Bayer Crop Science or thiamethoxam pesticide from Syngenta.
The study demonstrated that exposure to NCPs lowered the success of honeybee colonies over the winter period in Hungary and the UK. No harmful effects were observed on overwintering honeybees in Germany.
Across all three countries, increasing levels of NCP in the nests of the buff-tailed bumblebee and the red mason bee – both wild bees – resulted in reduced reproductive success.
“The neonicotinoids investigated caused a reduced capacity for all three bee species to establish new populations in the following year, at least in the UK and Hungary,” said Dr Ben Woodcock, lead author of the study.
The ecological entomologist suggested that the varying impacts on honeybees between countries could be linked to factors such as the availability of alternative flowering resources in agricultural landscapes for bees to feed on, as well as general colony health.
According to Professor Richard Pywell, co-author of the study, the effects of neonicotinoids have long been highly contentious with previous studies indicating neonicotinoid harm to bees criticised by the pesticide industry.
Pywell explained that this latest study is different as it was designed “to reflect the real world due to its size and scope”, spanning 2,000 hectares and factoring in bee disease, surrounding landscape quality, colony growth rate, worker mortality and overwinter survival.
“[The study] goes a considerable way to explaining the inconsistencies in the results of past research, as we were better able to account for natural variation in factors like exposure to the pesticide, bee food resources and bee health for different bee species,” he added.
Speaking to Greenpeace’s Energydesk, a Bayer spokesperson expressed the company’s disappointment with the way that the results were presented, and said that more environmental factors should have been taken into account.
Syngenta, also speaking to Energydesk, emphasised the findings of the study in Germany where neonicotinoids were found to have no impact on honeybees.
In September 2016, Energydesk revealed that Bayer and Syngenta had commissioned private studies that also showed that their neonicotinoids could cause serious harm to bees.
The EU brought in a temporary ban on the use of neonicotinoids on crops attractive to bees in 2013 due to links to the large-scale, long-term decline in wild bees across Europe.
Ireland voted against this proposal to restrict the use of three neonicotinoids, and recently moved to block a proposed ban on pesticide use in areas of farmland dedicated to increase biodiversity, called Ecological Focus Areas.