Thanks Eugene for the citation in Bee Culture.  I read that summary of primary work (also published in "Nature Scientific Reports", then went to the original paper (which is open access by the way).


The discrepancy you noticed is because Traynor et al monitored hives as they traveled through several pollination locations on the east coast USA over 300 days.  McArt et al were specifically looking at apple orchard pollination effects, they did not follow hives over an extended period nor were their study's hives moved during the study.   As Randy pointed out, levels of chemicals will change over the longer time and different locations in the Traynor study relative to the McArt one.


I thought about the fact that the hives being moved over 300 days were also being managed and this might involve swapping hive furniture among colonies.  This wasn't mentioned in the Traynor paper, so we don't know if they took that into account.  It probably didn't matter to the purpose of their investigation, because they wanted to monitor hives in the real-life situation.


“Our results fly in the face of one of the basic tenets of toxicology: that the dose makes the poison,” said Dennis vanEngelsdorp, an assistant professor of entomology at UMD and senior author on the study. “We found that the number of different compounds was highly predictive of colony death, which suggests that the addition of more compounds somehow overwhelms the bees’ ability to detoxify themselves.”


This comment speaks to Dick's assertion that different toxicities may not be additive.  In fact, sometimes they are multiplied instead.  Especially troubling is the potential for synergistic effects between many fungicides, which interfere with mitochondrial metabolism, and insecticides.  The fungicide is not supposed to be toxic to bees, but it works by inhibiting a mitochondrial detoxification pathway that all insects rely on, including bees.  For an excellent overview of this see:  http://scott.entomology.cornell.edu/145.pdf


Thus, when bees are exposed to both the fungicide AND an insecticide, the net effect may be magnified because the bee is unable to efficiently detoxify the insecticide since the fungicide cripples their P450 system.


Christina



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