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Insecticides used on flowering crops have major impacts on bumblebees

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New research from the University of Stirling, to be published in the top journal Science, sheds light on the causes of bee declines.

Declines in populations of wild bees, such as bumblebees, have led to great concern that yields of crops and the survival of many wildflowers may be threatened

Flowering crops, such as oilseed rape and sunflowers, are treated with neonicotinoid insecticides as a seed dressing to protect them against pests. The chemicals are systemic, travelling through the plant, and low levels are found in the nectar and pollen. The new research shows that bumblebee nests that were exposed to such low levels for just two weeks subsequently grew more slowly and showed an 85% reduction in the number of new queens they produced.

Neonicotinoid insecticides are the best-selling insecticides in the world, with global sales of over $1 billion, and they are broadly used on many different crops. Bumblebees forage over a kilometre from their nest to find food, so most bee nests in agricultural areas will be exposed to these compounds.

The work was supervised by Professor Dave Goulson at the University of Stirling. He notes: “Our work suggests that trace exposure of our wild bees to insecticides is having a major impact on their populations. Only queen bumblebees survive the winter to build new nests in the spring, so reducing the number produced by 85% means far fewer nests the following year. Repeated year on year, the long term cumulative effects are likely to be profound.”

The study was carried out by Dr Penelope Whitehorn and Steph O’Connor. Dr Whitehorn said “Bees are vital to farming and to wildflowers. There is a clear need to re-evaluate the safety of these chemicals.”

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