Peter Borst wrote about Brenda Ball's work:

> Deformed wing virus has become a damaging disease since the arrival of
> Varroa. ...Infected bees have reduced life expectancy and this can cause
> heavily infected colonies to die during the winter.
>
> it is necessary to kill the mites. This needs to be done before the
> end of summer so the colony ...
> * late July or early August *

I am surprised if everyone does not know this by now.  Dr Stephen Martin 
re-inforced this work in his lecture to the Central Association (UK) in 
November 2001.  I wrote about it in our newsletter in February 2002:
http://www.stratford-upon-avon.freeserve.co.uk/Newsletters/February2002.htm
see CENTRAL ASSOCIATION LEAMINGTON WEEKEND.

What is perhaps more important is the fact that when varroa first arrived 
here there was very little virus around - so large populations of mites 
could be sustained because they were not carrying the virus.  Since then, 
the virus has become much more widespread so it is much more likely that a 
mite will carry it.  The effect is like playing Russian roulette.  When 
varroa first arrive it was unlikely that the gun had any bullets - now it 
probably had a full chamber.
Stephen lectured on this in a follow-up lecture to BIBBA in 2007.  I wrote 
this up here:
http://www.stratford-upon-avon.freeserve.co.uk/Newsletters/May2007.htm
see VARROA TOLERANCE/RESISTANCE IN APIS MELLIFERA

Best wishes

Peter Edwards
beekeepers at stratford-upon-avon.freeserve.co.uk
www.stratford-upon-avon.freeserve.co.uk/





At Apimondia in 2005 we were told that colonies could easily collapse with 
just 1000 mites. 

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