I found this study to be of great interest, since it confirmed an
observation that I made some years ago when I was reviewing survival of
tracked colonies on the East Coast during the season.  One apple orchard
was a death trap for colonies--since few of the hives that pollinated that
orchard survived through the next spring.


> >The study demonstrates that the levels of insecticides and fungicides
> found in fresh bee bread among colonies pollinating apple orchards are at
> levels of chronic effect concern or acutely toxic, even though there were
> no sprays during bloom.


The above interpretation calls for a bit of elaboration.  The authors
collected pollen at only one time point at the end of bloom, and assumed
that the LD50's of all detected pesticides were additive (a not
unreasonable assumption).  That said, their Fig. 4 shows that for the 30
orchards from which samples were taken, that in only 5 of them did the
total hazard quotient exceed 20% of the oral LD50.

So yes, in 1/6th of the orchards, the collected pollen (coming largely from
flowers other than apples) might be cause for concern, and one would expect
the effect to be largely limited to the newly-emerged and nurse bees (which
can have serious short-term consequences).  In the other 5/6ths of the
orchards, one would expect to see little acute adverse effect, and due to
the short duration of exposure, perhaps little chronic effect.

What the study also indicates is that much of the pesticide exposure
appeared to come from foraging outside of the orchards, and based upon the
timing, some from planting dust.

The question remains as to why, despite the rapid turnover of pollen in the
hive during May, that some apple pollination exposures result in long-term
negative effects with regard to colony survival.

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

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