Bee colonies in North America and Europe
have been collapsing within a few weeks, leading to speculation that
neonicitinoid pesticides used as seed treatment to ward off insects are
responsible.
Now a research team in Australia has
found that there are multiple causes for the sudden death of colonies, confirming
what many Ontario grain farmers and others have been saying.
They are trying to stave off an Ontario
government goal to cut the use of neonicitinoids by 80 per cent.
But the sudden collapse of colonies has
convinced many that something such as pesticides must be to blame.
"When you get a colony failing like that, you're
not just seeing the death of individuals but the absolute collapse of a whole
society," said Dr. Andrew Barron, leader of the Australian research team
whose results have been published in Proceedings of the National Academy of
Sciences journal.
Rather than focus on the stress chemical exposure,
pests and pathogens had on individual bees, Dr Barron and his team wondered
what impact chronic stress was having on bees highly-sophisticated hierarchical
communities.
It is well known that honey bees delay leaving their
hive to forage until later in adulthood. Foraging for nectar and pollen is hard
work, and bees frequently die from exhaustion or getting lost.
But if external stressors such as pests or pesticides
kill too many forager bees at once, it triggers a rapid maturation of the next
generation and prompts them to leave the nest before they're are ready.
"Bees who start to forage when they've been
adults for less than two weeks are just not good at it. They take longer, and
they complete fewer trips," says the research team.
The team placed tiny radio trackers on young forager
bees and discovered they also died earlier.
When the team entered this information into a model
they found these premature deaths triggered a vicious cycle, whereby subsequent
generations of inefficient foragers could not return enough resources to keep
the colony going, leading to its collapse.
"Our model suggests bees are very good at
buffering against stress, but there's a tipping point and then you see this
rapid transition into complete societal failure," Dr Barron said.
Dr Barron said their findings are the first to propose
an explanation for the unusually rapid collapse of bee colonies.
