Agricultural ecology

Complex effects of pesticides on bees

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Honeybee colonies could be compensating for the harmful effects of certain pesticides by producing more workers, at least in the short term.

Some European countries banned neonicotinoid pesticides in 2013, but this remains controversial because field studies have failed to confirm the adverse effects reported for bees in the lab. Mickaël Henry at the French National Institute of Agricultural Research in Avignon and his colleagues positioned honeybee colonies in farmers' fields so that they were exposed to varying levels of the pesticide thiamethoxam. The team radio-tagged and monitored nearly 7,000 bees, and found that pesticide exposure caused an acceleration in death rate over time.

The colonies, however, compensated for dead foragers by producing more workers and fewer drones. This maintains honey production but could decrease bee reproduction in the long term. The risks of pesticides in the field may be best understood by studying entire colony cycles, the authors say.

Proc. R. Soc. B 282, 20152110 (2015)

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