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Discussion Starter · #1 ·
Friday, March 19, 2010 Widely Used Pesticides Found to Impair Bee Reproduction

Posted: March 8, 2010

By Janet Raloff, for Science News' Science & the Public Blog

Pesticides are agents designed to rid targeted portions of the human environment of undesirable critters – such as boll weevils, roaches or carpenter ants. They’re not supposed to harm beneficials. Like bees. Yet a new study from China finds that two widely used pyrethroid pesticides – chemicals that are rather “green” as bug killers go – can significantly impair the pollinators’ reproduction.
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Both chemicals are widely used in North America and elsewhere, including China. And, the researchers point out, the concentration of each pesticide that produced adverse effects in the experiments was at or below those that bees could encounter while pollinating treated crop fields.

In recent years, there’s been a big move by U.S. farmers to turn away from broad-spectrum potent bug killers to the more targeted and environmentally friendly pyrethroids. These synthetic chemicals have been fashioned after the natural pyrethrin bug deterrent in chrysanthemums.

The authors of the new study don’t argue that pyrethroids are a cause of colony collapse disorder, the mysterious die-offs affecting honeybees throughout North America. But they do argue that their findings suggest further investigation is warranted to confirm whether these immensely popular crop-protection chemicals might prove a previously unrecognized threat to pollinators. The source of a double-whammy, if you will, for already hammered bees.

Ping-Li Dai of the Chinese Academy of Agricultural Science and the Ministry of Agriculture led a team of researchers at those Beijing institutions together with a physiologist from the Second Military Medical University in Shanghai. The team investigated sublethal effects of bifenthrin and deltamethrin. Bifenthrin is used to kill everything from termites around homes to fire ants, corn pests and the mites that attack fruit trees. Deltamethrin is targeted at aphids, mealy bugs, whitefly, fruit moths, caterpillars on field crops, roaches, horseflies, mosquitoes and fleas.

After first establishing the dose that would kill no more than five percent of exposed bees, the researchers laced sugar water near bee hives with either of the pyrethroids at that tolerable dose. Worker bees had access for 20 days to the pseudo-nectar in each of three successive years. Queens in each colony were dosed every five days over each treatment period. Studied bees had no access to outside nectar during the trial periods.

Compared to queens receiving clean sugar water, those in the pyrethroid groups were substantially less fecund. For instance, clean queens in 2006 laid a little more than 1,200 eggs each day, compared to not quite 900 a day in the bifenthrin group and roughly 600 per day in the deltamethrin group. In general, the weight of eggs laid was higher in the pyrethroid-treated hives, but the hatch rate of pyrethroid-exposed eggs was significantly depressed. It varied by year, but in 2008, for instance, 88 percent of eggs in the control hives hatched versus 71.4 percent of those in the bifenthrin-treated hives and 80.5 percent of the deltamethrin-treated bees.

The success rate of hatchlings, that is the share that reached adulthood, varied from 75 to 95 percent in the control hive – making it between 20 and 40 percentage points higher than in hives where bees had been exposed to a pyrethroid. Dai and colleagues report their findings in the March Environmental Toxicology & Chemistry.

The bottom line, Dai’s team concludes: “The impact of pesticides on the colony may be severe.”

And the researchers concede that they can only guess at how severe because their paper focused on easily quantifiable, gross effects. Both pyrethroids are neurotoxic, typically causing paralysis and worse in target pests. The Chinese scientists didn’t investigate whether in-egg or juvenile exposures to the pesticides might have resulted in behavioral impacts during adulthood. Perhaps diminishing the bees’ ability to learn tasks or remember where good nectar sources were.

As I pointed out in a story four years back, pyrethroids may be relatively green – but they’re not totally benign to non-target organisms. That story was about little aquatic midges and other sediment dwellers. Essentially the food for fish and other critters people really care about.

Now we see threats to bees. And that should give all of us pause – because these unsung heroes of the farm make much of today’s bountiful harvests possible.


Now let me see, those pesticides that the British Bee Keepers Association endorse as being 'bee-friendly', aren't they pyrethroids?

And those strips they have been telling beekeepers to put in their hive to kill varroa, aren't they also pyrethroids?

So I wonder why this research was left to the Chinese to do?


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Discussion Starter · #3 ·
Comments by Dr L. R. B. Mann, a biochemist who served for its first dozen years on the Toxic Substances Board advising successive New Zealand Ministers of Health on poisons.

I wonder why these researchers didn't test a pyrethroid that is being deliberately inserted into many thousands of hives in many parts of the world, for the purpose of killing the awful pest _Varroa destructor_. The brand is Apistan.
I have examined the 1996 Extoxnet bulletin on toxicology of fluvalinate (the generic name for the active ingredient of Apistan®, Mavrik™, and several other branded commercial insecticides).
It is stated to be of the chemical family 'pyrethroids' i.e. its molecular structure is similar to those of the natural insecticides found in the famous African daisy _Pyrethrum_.
However, it is substantially different from natural pyrethrins. In particular, it contains 4 halogen atoms - 3 fluorine atoms and one chlorine atom - covalently bonded to carbon. This is a major drawback, on the experience with such compounds to date.
Such carbon-halogen bonds are very unusual in nature (and when they occur are typically toxic e.g. some natural antibiotics). The general drift of info accumulated since Carson's far-sighted 'Silent Spring' (1962) has been an increasing variety of disconcerting biological harm from such compounds. Organochlorines are, broadly speaking, bad news - especially when chronically absorbed. Organisms generally lack enzymes to metabolise them, and bioaccumulation is the rule. The Extoxnet bull lacks info on tests for such possibilities with fluvalinate. The stated rapid excretion is not the same as evidence on actual residues in the body.
The specific statements in the infosheet tend to read reassuringly, with the exception of high toxicity for fish and aquatic invertebrates (which would not obviously be exposed by use in beekeeping) . But my dozen years on the Toxic Substances Board taught me to distrust such claims by the chemical industry. Numerous pesticides got legal approval on the basis of such soothing reads - forged by Industrial Biotest Corp, whose top executives served years in jail upon conviction for faking these "results". The chemical industry is, as an historical tendency, a refuge for crooks. I could recount many detailed direct experiences consistent with this general pattern. Therefore, I for one disbelieve that fluvalinate has been properly tested or that the summarised claims are reliable.
My personal inclination would therefore be to disparage the concept that our beekeeping should adopt chronic - tho' not continuous - administration of any such organohalide compound to our bees.
The only statement about bees in the bull is:
> Fluvalinate was not toxic to honeybees
> exposed to residues left on cotton leaves after application of
> unltralow volume (ULV) and emulsifiable concentrate (EC) formulations
This is a very different mode of exposure from what prevails in a hive with strips of Apistan amongst the bees for a week or two.

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for those interested take a look at another thread Bayer Neonics Game Over?

which has a link to a newly published survey of bees, combs and bee bread, which SURPRISE shows that Fluvalinate is found in 98% of all 259 beeswax samples tested, and 88% of the bee bread and 83% of the bees tested.

furthermore some of the beeswax samples exceeded the LD50 level (level that is toxic).

meanwhile people are running around trying to blame gmo,s cell phones, farm chems etc - who would have guessed beekeepers were slowly poisoning there own hives with EPA legal chemicals?

its truly a bizarre situation. like the health care story in the news which is full of misinformation and conspiracy agendas, the honeybee crisis is similarily sidetracked with few people realizing some of the basic FACTS.
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