>From what you say, you do not consider a sublethal effect to be "colony
collapse", although that's what you hinted at when you shared your
impressions of one of the three neurotoxic-at-sublethal papers I listed
(the de Almeida Rossi? one)  and the van der Sluij review.

Sorry for being unclear.  A sublethal effect upon individual bees could
easily lead to complete colony collapse.  If a field bee's behavior is
changed such that it does not return to the hive, that would not be
considered as a toxicological "lethal effect," but if enough bees were
affected, the colony would quickly collapse.  That is what I was trying to
explain about understanding colony population modeling--it's all about the
intrinsic rate of increase (or decrease).  Sublethal effects to the
individuals that affected navigation, immunocompetence, longevity, or
altruistic self removal would quickly show up in the intrinsic rate of
growth of the population as a whole.

>
> >I further agree with you that honey harvest success on canola in western
> Canada means neonics are probably not significantly harming bees on canola
> in western Canada.
> But I cannot comfortably extrapolate, with you,  that this means bees are
> not suffering any effects from neonics on other crops in other places.
>

Christina, please be careful about putting words into my mouth.  I have
never said or implied that "bees are not suffering any effects from neonics
on other crops in other places."  I've published in my articles specific
neonic applications that are clearly problematic.  However, strong
independent data from the major field crops corn, soy, and cotton suggest
that the concentrations of residues in pollen and nectar (not in corn) are
in the same range as that of canola, so it would be completely reasonable
to expect that they would also have little negative effect on colony health.

>
> >The plant species, the type of treatment cocktail, the nature of the
> soil, the behavior of the insects at different latitudes, the weather, the
> local forage, and many more variables mean that "one size" does not
> necessarily "fit all"....at least, not until we prove it does.
>

As you well know, it is scientifically impossible to "prove" that one size
would fit all, since "all" could never be defined.  So the best that we can
do is to go with the tests involved with each specific registered use, and
then follow up studies in the real world when the product is actually
used.  This is exactly the situation for neonics--necessarily imperfect
registration by EPA, then continued testing in the field by both the
registrants and independent research groups afterward.

>
>
> >You are also measuring "field relevant dose" as the amount each bee
> brings to the hive, not the amount IN the hive.  So this means larvae,
> foragers, queens, and nurse bees are all potentially exposed to different
> levels of chems...but the ones considered "field relevant" are the forager
> levels.
>

The amount "in" the hive is determined by the amount brought by foragers,
so this would be the most realistic way to test.  I've posted a snip of a
recent graphic that I created of pesticide exposure pathways in the hive
http://scientificbeekeeping.com/pesticide-exposure-pathways/

The graphic shows how foragers take the main hit in most cases, minimizing
the exposure of the queen and brood (this is not the case with the
beekeeper-applied miticides).  A colony can absorb forager death better
than brood death, since the death of a forager has less effect on mean
worker longevity than does the death of a larva.  The reason that mean
longevity is so important is that it then affects the death rate (if mean
lifespan is reduced, the effect is then an increased death rate).  The
intrinsic rate of increase of a colony (for the benefit of the List) is a
function of the birth rate minus the death rate.

The take home message is that any toxin that has adverse effects on younger
bees will have more impact upon the colony than one that equally affects
older bees.  The point is that the sublethal effects that you are
justifiably concerned with will be strongly exhibited in the "r" of the
colony, and easily observed by tracking the rate of adult population growth
or decline.

--
Randy Oliver
Grass Valley, CA
www.ScientificBeekeeping.com

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