Neonicotinoids are partial contraceptives for male honeybees

Pollen tainted with neonicotinoid pesticides could interfere with honeybee reproduction.

After eating pollen spiked with thiamethoxam and clothianidin, males made almost 40 percent fewer living sperm than males fed clean pollen, researchers note in the July 27 Proceedings of the Royal Society B. The pesticide concentrations, 4.5 parts per billion and 1.5 ppb, were in the range of what bees encounter around crops, says coauthor Lars Straub of the University of Bern in Switzerland.

Conservationists have raised concerns that chronic exposure to neonicotinoids is weakening honeybee colonies. 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.