Pollen tainted with neonicotinoid pesticides could interfere with male honeybee reproduction, a new study finds.
After bee colonies fed on pollen spiked with the pesticides thiamethoxam and clothianidin, male bees, or drones, produced almost 40 percent fewer living sperm than did males from colonies fed clean pollen, researchers report July 27 in Proceedings of the Royal Society B. The concentrations of the pesticides, 4.5 parts per billion and 1.5 parts per billion, respectively, were in the range of what free-living bees encounter when foraging around crops, study coauthor Lars Straub of the University of Bern, Switzerland, says.
Pollinator conservationists have raised concerns that chronic exposure to neonicotinoids widely used on crops is inadvertently weakening honeybee colonies working the fields. The amount of sperm males produce might affect how well a colony sustains itself because young queens mate (with about 15 males on average) during one or two early frenzies and then depend on that stored sperm for the rest of their egg-laying years. The new study is the first to examine neonicotinoid effects on honeybee sperm, Straub says.