A new study sheds some light on the declining numbers of bee colonies around the world. It discovered that some of the blame lies with common insecticides which lowers the amount of live bee sperm produced by males. This leads to a lower bee population by reducing the queen’s efficiency to lay eggs and maintain a colony’s population.
The research team from the University of Bern, Switzerland have discovered that a certain type insecticides, neonicotinoids, do not directly kill bees, but they just make it harder for a colony to grow. The researchers observed in a controlled experiment that drones that came in contact with the chemical, most commonly by eating treated pollen, had 39 percent less live sperm than usual.
Although, the drones affected by the pesticide and those who were not, produce the same amount of sperm, the difference between them was the quality of the sperm. Examining it under a microscope revealed that the bee without any insecticide in her system produced on average almost 2 million living sperm, while those who did only had about 1.2 million sperm count. The affected bees also had an 8 to 11 percent lower sperm viability which takes into account the percentage of living versus dead sperm. Queen bees use only the living sperm to fertilize eggs.
More research in needed to fully understand how lower sperm availability might affect a colony’s reproduction rates. The researchers think that without enough viable bee sperm, a queen can’t lay sufficient eggs or she will have to leave the safety of a hive to go get more sperm from mating with other drones, exposing herself to danger in doing so.
Exposure to pesticides and their various effects are not the single cause of the decline in bee colonies. Other important factors include disease, parasites, and habitat loss. The combinations of these factors have led to 30 percent loss of colonies each year in North America and Europe, over the past decade.
The insecticide that is causing the drones to produce lower quality sperm, neonicotinoids, were introduced in the late 1980s as a safer alternative to even more toxic insecticides. Currently, the U.S. Environmental Protection Agency is evaluating this class of pesticides for potential harm to various pollinators.
Should we pay more attention to the health of pollinators or that of crops?
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