> there is a large difference in "defending" the use of a product, and the
discussion of whether or not it is effective.
> >I have given plenty of evidence that it is not.
>
Others have given plenty of evidence that it is. Pete, there is clearly
not a cut and dried answer to the question as to how effective treatment
with fumagillin is in reducing colony mortality or increasing productivity,
now that the primary nosema species in most areas is N ceranae.
In the few experiments that I've run, I've gotten mixed results.
Surprisingly, in one trial (as yet unpublished) of 36 hives, treatment of
colonies reduced mortality, although nosema spore counts were not high
across the test colonies. There was only one replicate, so can't reach a
firm conclusion.
In another trial, weekly drenching with fumagillin helped to reduce spore
counts in spring compared to other products tested, but still did not
prevent spore counts from going up sharply.
Across the larger body of research in the literature, I generally see that
fumagillin has some positive effect against N ceranae and upon colony
strength.
But in my own operation, although N ceranae is certainly present,
especially in winter, I cannot find any strong correlation between between
the level of nosema and loss of colony strength over winter.
On the other hand, when I survey colonies, my strongest and most productive
colonies are rarely infected above a trivial level, whereas my weaker and
less productive frequently are infected. But I don't know whether N
ceranae is causal, although I certainly suspect that it would have a
negative effect, due to its unambiguous negative effect upon energy and
protein metabolism, and its demonstrated inducement of early foraging
(leading to shorted bee lifespan).
--
Randy Oliver
Grass Valley, CA
www.ScientificBeekeeping.com
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