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Informed Discussion of Beekeeping Issues and Bee Biology

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From:
randy oliver <[log in to unmask]>
Reply To:
Informed Discussion of Beekeeping Issues and Bee Biology <[log in to unmask]>
Date:
Mon, 3 Sep 2012 12:43:59 -0700
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>
> >if I observe mite infestation rate to exceed 5%, I consistently see virus
>> infection in the broodnest. If I keep the mite infestation down to less
>> than 2% at highest (lower for most of the season), then the brood remains
>> healthy.
>>
> Is this your own experience?  Are there other references/experiences about
> treatment thresholds?
>

Umberto, there is a large body of thresholds.  Look at ScientificBeekeeping
varroa IPM Reconnaisance for dated ones.  Most of us commercial beekeepers
now use much lower thresholds.

The 2% figure came from limited studies that found that naturally resistant
bees appear to attempt to hold mite levels to about that level.  I'm sure
that this is a ballpark figure, but is perhaps the point of diminishing
returns.  It works for my operation, and it is my personal experience that
I start to see virus problems at about 5% infestation (again ballpark, as
neither the bees, the mites, nor the viruses keep track).  At 15% you can
kiss the colony goodbye.

The above figures apply to my bees, in my operation, in the foothills of
the Sierra Nevada around Grass Valley, CA, which may be similar to your
Italian climate.  Have you got any data or observations to share for Italy?

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

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