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Subject:
From:
Wolfgang Pöhlmann <[log in to unmask]>
Reply To:
Informed Discussion of Beekeeping Issues and Bee Biology <[log in to unmask]>
Date:
Wed, 3 Mar 1999 22:01:19 +0000
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Hello,
I mostly agree with Madeleine Pyms explanation of the "whom" and slow
collape of varroa infested colonies.
There are two ways in wich the number of mites in a colony increases.
1. by breeding mites. As long as a colony has brood the mites can
enter the brood cells before capping and reproduce. The rate of
increase of mites  per brood cell depends on the season
(infertileties)  and on whether it was a worker cell or a drone cell
(time of capping). It can be roughly estimated that the mite
population doubles every month with brood in the hive.
2. by reinvasion. From collapsing hives in the neighbourhood. I also
had problems with this 3 or 4 Years ago when a beekeeper less than 1
km apart from my colonies lost his 6 hives, that he all bought two
year ago. He said that they brought a good honey crop , but they all
died. He was not serious enough about monitoring and treating for
varroa.  Next year I had high number of mites.   In an article of
Imhof et al I found a diagram where they measured the reinvasion rate
over one year. It is normaly relativ low but shows a peak in August.
It can be as high as 300 mites per day. The autors state that this
is caused by robbing and bees flying to a wrong hive.
The most likely time for a collapse from varroa is late summer or
autumn. Assume a colony has 500 mites in winter and starts breeding
in march (my location). The bees increase their broodnest up to june
to say 30000 brood cells. The mites have increased to 4000. This
means that one of 8 cells is parasited, and the hatching bee will
have a smaller lifespan. Frome june on the brood area gets steadily
smaller until November, when we will find no brood in our colonies.
Now assume that we have half the brood area in August, that means we
have 15000 brood cells and 16000 mites. So roughly every broodcell
contains a mite. Some cells are even parasized by more than one mite.
If these bees do hatch they will have deformed wings or other
defects. This colony is colapsing. The continued increase of the mite
population and the reduced brood area of the bees in summer and fall
make this time  most dangerous for the colonies.  And it are the
strongest (most brood) colonies that die first!
Every beekeeper that has his hives in a varroa area should monitor
the population and treat accordingly. This is important. With
Madelaine Pyms old chinese wisdom and the situation with my not
serious enough neighouring bekeeper I was remindet to a word of one
of my teachers: "Nobody is useless. At least he can serve as a bad
example".
Greetings Wolfgang
Wolfgang Poehlmann
Alte  Schoeckinger Str.11
D-71282 Hemmingen

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