In a message dated 5/2/00 3:14:49 PM Pacific Daylight Time,
[log in to unmask] writes:

> The losses increased at a rate in proportion to the land treated- and
>  its ability to remain active in soils long after its application, plus
>  the resulting metabolites being highly toxic to bees.
>  What type of bee activity did the bees show whilst working your
>  harvests- efficient nectar collection?,ability to work in all positions
>  or just about 30° from the horizontal.
>  OK, you might have a bad case of Acarine, or/and resistant V.j.- I hope
>  so! But I f you have Imidacloprid in the area- investigate very
>  carefully.It must be stated that Bayer are of course  in total
>  disagreement with the independent results that are building up against
>  their product.

     I've not had experience with Imidacloprid, Peter, and I'm not sure it's
used in the US. (Those in the sunflower regions, please comment!)

    But I have always thought that more of our winter losses than we realize
are pesticide related.  Contaminated pollen can easily be stored away in
hives, even sometimes covered with fresh clean pollen in the fall, so that
there are no noticeable losses occurring late in the season.  If there are
losses, they would primarily be to young nurse bees/brood, so it would have
the effect of bringing an older population of bees into winter. (Taking
supers off to treat before the fall flow and allowing the brood chamber to
plug up with honey will also cut out that last brood cycle, with the same
effect.)

    When bees have continuous supplies of fresh pollen (especially high
quality ones, like goldenrod) they are able to deal with some stored pollen,
because the effect is diluted.  However, during winter, if no pollen is
available, the bees become extremely vulnerable to poisoned pollen, whether
it is Imidacloprid, or any other.  One reason that southern bees do not often
have such winter losses, is the continuous pollen throughout the winter,
which dilutes the effect of poisoned pollen, and enables the bees to get the
old pollen cleaned up before the spring buildup.

    Many beekeepers will take their lumps, clean out the hives, and reinstall
bees, without giving much thought to the reasons for the loss (or the
thoughts may just be so much speculation).  Take some time to carefully look
at the deadouts.  Did they go into winter with old bees?  Was there any
evidence of pesticide poisoning last season (particularly late poisoning from
sweet corn spraying (goldenrod in margins?), mosquito spraying, or whatever)?
 Just as some have mentioned, reference to tracheal mites is pretty much
useless speculation, unless one looks at the bees to see if the evidence is
there.

     Testing for contaminated pollen is expensive. But there is a cheaper
test, if you will take the time.  Select some frames with a lot of pollen
from the deadouts. Then put one of these frames right up against a frame with
mostly open brood. Go back in three days and see if the brood has become
spotty, as if the queen has a failing pattern of laying.  If you do this to
ten hives during the spring buildup, and ten hives get a spotty brood
pattern, you ought to become very suspicious of contaminated pollen.

    Another thing.  When you get a pesticide hit, no matter how minor, make
sure it gets reported to your pesticide regulators, and insist that the
investigator take samples of stored pollen from the comb, along with samples
of the dead bees, and plant tissue samples from the suspected application
area. Many will not do this, unless you insist.  If the bees recover, but the
pollen is contaminated, you will still be facing the pesticide losses later,
when bees are more vulnerable.

   Peter, you say:
>What type of bee activity did the bees show whilst working your
>  harvests- efficient nectar collection?,ability to work in all positions
>  or just about 30° from the horizontal.

    Would you elaborate further on this. I'm not sure I fully understand what
you mean?

Dave Green
The Pollination Home Page:  http://pollinator.com