>
> >Doing a very rough conversion, assuming steady-state and using a 100-day
> mite time to live, that gives us a 5000 mite number, mostly phoretic at that
> date, I assume.
Allen, I feel that your total mite estimate is likely a bit high. I checked
with various conversions, e.g.,
https://secure.fera.defra.gov.uk/beebase/public/BeeDiseases/varroaCalculator.cfm
and come up with estimates of 2500-3500.
>
> >Anyhow, this is very rough, so take the 5,000 and a late October
> population of 30,000 (8 lbs. of bees) and we get 5/30=17%.
So phoretic infestation level may well be as little as half of your rough
calc, or 8%. However, your estimate of 30,000 bees may also be high, which
would then raise the infestation percent (this is one reason that I prefer
alcohol wash to natural mite drop).
>I think that any commercial beekeeper could have saved him the effort, and
most would halve that number or quarter it.
He wasn't trying to see determine a threshold, that figure simply came out
of the data from the control and non miticide treated hives. Below 50
mites, a substantial number survived and made grade in almonds. Above that,
you might as well save yourself effort and walk away from them.
>
> >Seems we calculate differently. I'd be interested in how 20-30 converts
> to 3%. in your situation. I gather we are using different assumptions.
See above.
> > I checked the drop against washes in my outfit last year and got a good
> fit with my method and timing, albeit on a small sample.
I have done on a larger scale, and came up with a coefficient of correlation
near zero! Really surprised me. That was when I gave up on natural mite
drop as being meaningful if not taken over a long series.
>
> > I guess that answers my questions about history and location.
>
This was separate from Frank's trial. His was in southern California
hills, well south of Bakersfield.
>
> >One huge caveat in this is the use of packages. They are a special case,
> and seem to have less vulnerability to varroa collapse than overwintered
> colonies, possibly due to different virus profiles (which is confirmed
> anecdotally). I suppose that may explain why most of us would think hat 50
> is twice too high and maybe 4X.
>
Sorry if I misled. Eischen's data was separate from the CAP project, which
was packages. Eischen's was with commercial migratory hives. However, I
agree with you on the virus issue!
Randy Oliver
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