> Who has looked? Who has data?
I have the data, hundreds of files. Plenty of people have looked, but the figures are dismissed by those who wish to believe otherwise. We have seen that clear enough here and elsewhere
First, Jim Frazier et al:
Generally, the lowest observed sublethal effects for imidacloprid in the lab are at 1 ng/bee which is equivalent to 10 ppb for an average 100 mg bee. Achieving a 10 ppb dose would require consuming pollen with residues of 250 ppb imidacloprid at a consumption rate of 4 mg pollen/day (4% of bee’s body weight). This high residue level is never found when label-rates of Gaucho are used as a seed treatment (generally 1-5 ppb in pollen). Nectar residues of imidacloprid are usually less than in pollen, although more is consumed over the bee’s life.
However, even if a forager ingests 10% of their body weight in nectar per day, it would require 100 ppb of imidacloprid in the nectar to achieve a 10 ppb dose per day, regardless of the high turnover rate of this water-soluble insecticide in the bee. Imidacloprid is known to be rapidly metabolized and is excreted by adult bees with a half-life of about 5 hours (Suchail et al., 2004). This means that more than double the above doses of imidacloprid in the food is required to maintain a body level that keeps up with its rapid clearance from the bee. It is unlikely that doses of neonicotinoids from routine sys-temic seed treatments will attain the necessary > 100 ppb levels in pollen or nectar to acutely impair honey bees.
Pesticides and Their Involvement in Colony Collapse Disorder
by JIM FRAZIER, CHRIS MULLIN, MARYANN FRAZIER and SARA ASHCRAFT Department of Entomology; Penn State University, 501 ASI Building, University Park, PA
Jointly published in the American Bee Journal and in Bee Culture, August 2011
Then Cresswell compiles and collates all the data:
Imidacloprid has been assayed in nectar from sunflowers
(Decourtye et al. 2003 ; Schmuck et al. 2001 ), in nectar
from oilseed rape (Bonmatin et al. 2005 ) and in the honey
sacs of honey bees foraging for nectar on P. tanacetifolia
(Wallner et al. 1999 cited in Decourtye et al. 2003 ). Based
on these reports, the field-realistic range of imidacloprid
concentrations is assumed to be 0.7–10 ugL -1.
Cresswell (2011) Ecotoxicology 20:149–157
More recently:
In general, the few reported
residue levels of neonicotinoids in nectar (average of
2 ug kg -1 ) and pollen (average of 3 ug kg -1 ) were below
the acute and chronic toxicity levels; however, there is a
lack of reliable data as analyses are performed near the
detection limit. Similarly, also the levels in bee-collected
pollen, in bees and bee products were low.
Neonicotinoids in bees: a review on concentrations, side-effects and risk assessment
Tjeerd Blacquiere et al. (2012) Ecotoxicology, 21(4), 973-992.
This last reference points to the fact that the levels are so low as to be nearly undetectable. Of course, some will say not being able to detect them with the highest powered tools imaginable doesn't prove they aren't there.
Pete
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