PARIS: Farm pesticides killing more bees – study

PARIS: Agricultural pesticides sold to
farmers ready-mixed into “cocktails” can kill twice as many bees,
according to an analysis of 90 studies.

Each
measured the impact of environmental stresses such as pesticides and poor
nutrition.

And they
say commercial formulas, which contain multiple chemicals, should now require
their own licences.

“Exposure
to multiple pesticides is the norm, not the exception,” Dr Harry Siviter,
from the University of Texas at Austin, who led the study, told the BBC Radio
4’s Inside Science programme.

One 2016 study showed bee colonies containing larger
numbers of pesticides were much more likely to die.

“If
you have a honeybee colony exposed to one pesticide that kills 10% of the bees
and another pesticide that kills another 10%, you would expect, if those
effects were additive, for 20% of the bees to be killed,” Dr Siviter said.

But a
“synergistic effect” could produce 30-40% mortality.

“And
that’s exactly what we found when we looked at the interactions,” he said.

“So
we really should consider the interaction between those chemicals” when
licensing commercial formulas for use, Dr Siviter said.

“We
don’t continue to monitor pesticides once they’re licensed for use, so we’re
proposing post-licensing observations.

“If
those pesticides [used in combination] harm bees, that harm is recorded.”

‘Resistance increasing’

Another
study published this week, however, suggests bees around the world are
developing the ability to “clear out” a particularly damaging
parasite – varroa, a mite that lives and feeds on honeybees and larvae.

Bees
already have complex organised hygienic behaviours, such as removing infected
broods of larvae from the hive.

And now,
data published in the Royal Society journal
Proceedings B, from 40 years of research into colonies that survive
infestations, without any chemical treatment, reveals they are evolving to
“repurpose” that behaviour against varroa.

“We’re
seeing this resistance increasing around the world,” Isobel Grindrod, from
the University of Salford, said.

“And
we’re also seeing an increase recently in bee-keepers not having to treat [the
mites] with chemical treatments.”

“Pressure”
from the mites was driving healthy bees to adapt, she said.

“Their
adaptability is really important, and that’s why we need to maintain healthy
bee colonies – to keep that adaptability – because there will be other, new
diseases and pressures in the future.”