Underestimated Danger

The gut bacteria Nosema affects worker bee activity

Aug 12, 2015
If worker bees do not collect enough pollen, the whole hive is weakened.

If worker bees do not collect enough pollen, the whole hive is weakened.

A comparatively harmless infection with the gut bacteria, Nosema apis, reduces honey bee performance, researchers at the University of Western Australia have discovered. They monitored how the infection affects the natural foraging behavior of honey bees. Their studies revealed that sick honey bees cannot perform services as healthy bees do. They spend considerably less time on searching for pollen and nectar and they carry less food per flight back to the hive.

The researchers fed healthy worker bees with Nosema spores taken from infected bees. They then glued radio transmitters onto the back of the artificially infected bees and placed them back in their hive. They also attached transmitters to healthy bees. All four observed bee colonies contained 120 infected and 120 healthy bees – all together the scientists tagged and tracked 960 worker bees for several days in the field and collected data. They observed the bees’ activity, their orientation, choice of flower,  time of flight and also how many pollen grains the bees collected.

"No one had looked at bees at this level before, to see what individual bees do when they are sick," said lead researcher Dr Lori Lach. Her team discovered that the bees’ foraging behavior changed remarkably: They started foraging later and died earlier, so within their lifetime they foraged outside less often. And even if they did fly out, the bees collected less pollen.

“The species of Nosema used in the study (Nosema apis) has long been thought to be benign compared to many other parasites and pathogens that infect honey bees, and no one had previously looked for the effect of Nosema on behavior with such a low dose”, said Dr Lach. The scientists revealed that Nosema is a distinct threat to honey bee colonies. The reduced activity of worker bees weakens the whole hive. Bee researchers now have to develop suitable measures against the gut bacteria.

In the scientific study “Parasitized honey bees are less likely to forage and carry less pollen” you will find detailed information on the design and results of the study.

You can also read another article in Science Daily.

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