There has been quite a bit of confusion and a number of unfortunate
statements made, so let me bring everyone up to speed on what both Jerry B.
and I hinted at earlier.
I now have permission from Galen Dively of U MD to summarize his "overall
findings" as presented at last week's invitation-only NAPPC meeting, so long
as I do not divulge any specific data sets or data summaries, such as charts
or graphs.
Dr. Dively asked me to stress that the findings presented at the NAAPC
conference were only the first year of a multi-year study. They intend to
repeat the entire process in 2009 to confirm their findings. Galen Dively,
Mike Embry (of U-MD) and Jeff Pettis (of USDA) will be co-authors of the
paper that will result.
I'm going to keep it simple, so as to not introduce errors or
misunderstanding due to my choice of words. The purpose of the study was to
look at actual working colonies of bees exposed to imidacloprid. The study
was funded in part by the Burt's Bees grant that NAPPC administered.
They randomly assigned each of 30 nucs to 3 different treatment groups:
a) Control Nucs fed pollen patties with zero imidacloprid
b) Nucs fed 5 ppb imidacloprid in pollen patties
c) Nucs fed 20 ppb imidacloprid in pollen patties
The nucs were set up in an area with very little agricultural land to avoid
any other pesticides. The bees consumed 30 grams per day of the pollen
patties. Pollen traps were fitted to minimize the amount of natural pollen
brought in. The pollen patties were fed starting in May and for 11 weeks (2
full brood cycles). They monitored a number of variables during the
pollen-patty feeding and for months afterward:
a) Amount of pollen brought in
b) Number of foraging bees returning per unit time
c) Amount of capped brood
d) Overall colony strength
There were no differences in colony performance between the treatments.
The 20 ppb colonies and 5 ppb colonies are still doing fine and they are
combining the nucs and will monitor them over the winter. None of the
colonies died out.
No foraging bees got lost and couldn't find their way home. Everything is
entirely normal about them.
The conclusion presented was that imidacloprid alone doesn't affect bee
colonies, even at levels like 20 ppb, and even when bees are force-fed that
level for extended periods like 11 weeks straight.
Below is my analysis:
====================
Rather than any sort of "rock your world" results, these findings are in
agreement with the prior work that some have dismissed as "Bayer-funded
studies".
The findings confirm and agree with the prior findings of Kemp/Rogers
(2001-2004), Scott-Dupree/Spivak (2000), Elzen (2004), and
Cutler/Scott-Dupree (2007).
The findings are in stark contrast to what was reported in the "Palm Beach
Post", but it seems that the reporter could not even quote Jamie Ellis
correctly,
so I think we should wait for something on genuine U-FL letterhead before we
rush to the lifeboats in fear of the "tip of the iceberg" Bob thought he
saw.
So, to summarize, my understanding of the current scientific consensus on
imidacloprid is as follows:
The imidacloprid acute oral LD50 for bees is 192 ppb.
At very high levels like 500 ppb, one can start to see "memory and learning"
effects, but such high doses are also fatal.
At 50 to 100 ppb, multiple studies have shown various negative impacts on
honey bees.
At 20 ppb and below, there coninues to be a lack of any detectable problems.
No one has claimed that bees would be exposed to levels anywhere near 20 ppb
in the field. Most people toss around "typical" numbers like
"5 ppb" as a worst-case number.
Long-term exposure does not imply a significantly greater risk than
short-term exposure as neonicotinoids are rapidly metabolized by bees
and do not bio-accumulate. In something between 4 and 24 hours there are no
detectable residues left in the bees.
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