Bioaccumulation of fipronil more lethal than neonicotinoid imidacloprid

Recently in Cape Town we have seen the overnight deaths of hundreds of thousands of honey bees being attributed to the use of fipronil combined with molasses on vines to control ants.  While the science has been indicating that fipronil is the cause, in fact wine farmers found this concerning.  Lars Maack Owner of Buitenverwachting wine told the Weekend Argus that they are “very concerned” about the dying bees and said that “what is puzzling is that the current ant control programs were in place for the past eight years with no significant effect on beehives.”

The answer to this riddle may very well lie in this latest research finding.

Researchers in the UK reports Chemical & Engineering News, have “new evidence that the pesticide fipronil, not the neonicotinoid imidacloprid, caused a massive die-off of honey bees in France from 1994 to 1998. Both pesticides hit the market in the early 1990s.” At the time of the honey bee deaths in France, beekeepers and environmentalists put the issue at imidacloprid’s door, now research indicates that fipronil which is used on sunflowers is more likely the issue. Why? Philippa Holder and colleagues at the University of Exeter and Fera Science, found that “bees rapidly eliminate imidacloprid from their bodies, but they bioaccumulate fipronil. So over time, after prolonged exposure, fipronil becomes more lethal to them.”

The report continues that “the scientists quantified the toxicity of both pesticides to honey bees and used bioassays to determine the likelihood that they would bioaccumulate in bees. They then incorporated the information into a simulation to predict mass mortality in a honey bee population at environmentally relevant concentrations.” And now suggest that pesticide regulators around the world should pay heed to the need to discriminate between bioaccumulative and nonbioaccumulative pesticides.

In the report Holder states that “the potentially severe impact of dietary fipronil highlights the need to identify agrochemicals that cause time-reinforced toxicity, meaning they bioaccumulate and increase in the body over time”.

It is worth noting that fipronil was banned in the European Union for use on crops in 2017, the issue is that there are seeds treated with it that still find their way into market.  In South Africa and many other countries, it is still legal to use it as a common treatment for the control of ants, cockroaches, termites, fleas and ticks.

If we want to secure the future of our honey bees, is this yet another toxin that needs to go?

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