A new study has found that exposure of neonicotinoid pesticides affects the pollination services provided by bumblebees, resulting in the decrease in crop quality of apple trees.
The new study by the University of Guelph, environmental sciences professor, Nigel Raine, and other researchers, was published last week in Nature.
The study shows for the first time that exposure to field levels of a pesticide can reduce the pollination services bumblebees deliver to apples.
Bumblebee colonies exposed to a neonicotinoid pesticide, the most widely used group of insecticides worldwide, provided lower visitation rates to apple trees and collected pollen less often.
The latest study also showed that these pesticide-exposed colonies produced apples containing fewer seeds, demonstrating a reduced delivery of the bumblebees’ pollination services.
Studies had previously found that neonicotinoid pesticides affects bee behaviour, including pollen collection, learning performance and reproduction.
The new findings indicated that the reduced pollination delivery is not due to pesticide-induced changes in individual behaviour, but rather effects at the colony level – contrary to other recent findings by French researchers – that argued that pesticides don’t cause damage at a colony level; findings which have been widely touted by pesticide manufacturers such as Syngenta.
In April 2013, the European Union commenced a two year trial ban of certain times of neonicotinoid pesticides. But earlier this year, in a move opponents described as “scandolous”, the ban was temporarily lifted, by the UK Department for Environment, Food and Rural Affairs (Defra) for certain parts of England for use on oilseed rape crops following an ’emergency application’ by the National Farmers Union.
At the time, Prime minister David Cameron defended the move. “We should follow the science,” he said.
The move was also seen as particularly hypocritical with the UK’s contribution to the 2015 World Expo in Milan entirely focused on bees and beehive health (see video below).
Economic importance of bees
The new study shows for the first time the effects neonicotinoid pesticides has on the ability of bumblebees to provide their pollination services to help in the harvest of apples, a crop which has such a significant importance to the global economy.
More than 75m tonnes of apples are harvested annually by 95 countries, with scientists such as Raine stating that pollinators contribute nearly $500bn annually to the global agricultural economy.
Apples benefit from bee and insect pollination with factors such as seed number, fruit set, fruit size and shape all affected and influenced by pollination services.
To undertake the recent study, Raine and his fellow researchers exposed 24 bumblebee colonies to levels of neonicotinoid pesticide thiamethoxam that would be found in the field.
The experiment mimicked spring pollination conditions and included control groups.
Raine said the findings were concerning in that the effect of pesticide use on bees and subsequent inability to properly pollinate would not only affect the future production of apple crops, but other agricultural items as well.
“If exposure to pesticides alters pollination services to apple crops, it’s likely that other crops, particularly fruits, vegetables and nuts, and diverse wild plants that rely on bumblebees could also be affected,” he said.
“This makes our study both useful and translatable in a much broader context when considering the potential impacts of pesticide exposure on the pollination services provided by bees.”
But it’s the impact felt on the bees’ actual population, rather than their pollination ability, which has prompted dozens of groups in the US to ask the Obama administration to bolster regulations of pesticides.
The groups argue that pesticides have led to sharply declining populations of honeybees and other helpful insects.
The letter to the Obama administration asking for stricter pesticide regulations is signed by 128 groups, and calls on the Agriculture Department and the Environmental Protection Agency (EPA) to take immediate action to regulate the use of neonicotinoids.
The letter called for immediate action from the EPA.
“While we recognize the importance of a thorough evaluation of risk, in the case of neonicotinoids, EPA does not have the luxury of taking its time,” it read.
“The concerns…demonstrate the need for immediate intervention to mitigate risks and for increased oversight for the long term.”
While honeybee populations have declined for decades as a result of insecticide use, habitat loss and disease, researchers suggest neonicotinoid pesticides that have been commonly used since the 1990s contributed to sharper declines in recent years.
The White House estimates honeybee pollination contributes more than $15bn annually to the nation’s agricultural economy.