"bryan Clements" <[log in to unmask]> wrote:
>I was recently in a yard of bees that had tested positive. At the first test
>the worst board  had 50 mites and every other board had 5 or 6 mites. 50% of
>the yard had sticky boards. We visited the yard two weeks later and
>inspected 75% of the hives. We used the brood fork and did 6 digs into brood
>in each hive. Made a great mess. We looked and looked everywhere and did not
>find one mite. There was no drone brood present.
>To me it appeared as if the sticky board test was very accurate and that
>finding mites in a yard with light infestation was impossible with the eye,
>even when digging out brood.


        This report is interesting, but I interpret it differently.
        On their face, these facts suggest the colonies in question had rid
themselves of varroa, down to a low level if not entirely, during the
fortnight in question.  The simplest hypothesis would be to credit the
Apistan with having achieved this, but I don't find this plausible.
        If we had been able to keep Dr Denis Anderson here, he'd be across
into this yard tomorrow.  Perhaps we can lure him back from Australia for
more of the time.

        The complete absence of drone brood is itself interesting.
        Is there some suggestion that varroa cannot breed with comparable
efficiency in worker brood?

        The insensitivity, more accurately called a high threshhold, of the
Apistan/stickyboard test is beyond dispute, isn't it?  Of course, one has
to say 'compared with what'.
        One can imagine a hive that has many adult mites but for some
unknown reason has few or no mites in the brood.  A colony in that
condition will register positive on the strip/board test.  But the greater
fear has been scoring negative on that test while many mites are breeding
up but not yet capable of falling onto the sheet (or of being poisoned by
the Apistan) because they're sealed in capped brood.  In that condition,
the hive will have a high threshhold or severe insensitivity on the
strip/board test.
        I have been assuming this latter is the more common situation.  Any
expert correction?

R

-
Robt Mann
consultant ecologist
P O Box 28878   Remuera, Auckland 1005, New Zealand
                (9) 524 2949