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A new study carried out by researchers from the Royal Holloway University of London, the University of Reading, England and the University of Guelph, Canada suggests that use of neonicotinoid pesticides harms the abilities of bumblebees to apple trees, thus affecting the quality of the fruit and farmers’ crop yields.

Neonicotinoid pesticides are the most widely used pesticides in the world. Some earlier studies have revealed that these pesticides can affect the behavior of and impact their performance in learning, reproduction and pollen collection. However, critics of these studies dispute the findings. The European Union has restricted the use of some neonicotinoid pesticides, including thiamethoxam, in recent years, however, these pesticides are still permitted in the US.

Bumblebees are one of the most important pollinators of apples and several other crops across the world. Every year, over 75 million tonnes of apples are harvested globally, and insect plays a major part in determining the size and shape of the fruit. A study was done last August on honey bees with tiny trackers. The new study shows that the ability of bumblebees to pollinate apple trees gets affected when they are exposed to certain levels of neonicotinoid pesticides.

“Until now, research on pesticide effects has been limited to direct effects on bees themselves. This information provides a new perspective when trying to fully understand the trade-offs involved when deciding whether to use insecticides.” said study leader, Prof Nigel Raine, who works as environmental sciences professor at Guelph’s School of Environmental Sciences.

In this study, 24 colonies of buff-tailed bumblebee (Bombus terrestris) were exposed to thiamethoxam pesticide. The exposure levels were similar to those found in apple farms. Three groups of bees were used in the experiment. The first two groups were exposed to two different levels of thiamethoxam actually used by farmers (2.4 parts per billion and 10 parts per billion). The third group was not exposed to any pesticides.

Scientists observed that bumblebees exposed to visited and collected pollens less frequently compared to the unexposed insects. Colonies that got exposure to 10 parts per billion experienced the strongest effects. It was also found that apples produced by neonicotinoids-exposed bumblebee colonies had lesser number of seeds (36% lesser seeds), meaning the fruits were of inferior quality and there was not enough pollination as required.

“One of the important things about our work is that it highlights the importance of pollination services.” said Dara Stanley, a researcher at Royal Holloway University of London.

This research was funded by The W. Garfield Weston Foundation, U.K. Insect Pollinators Initiative, the Department for Environment, Food and Rural Affairs, Natural Environment Research Council, the Scottish Government, and the Welcome Trust. The detailed findings of the study have been published in the academic journal Nature.

 

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