There are always going to be individual mites that can tolerate higher doses
of a pesticide than others within the same population. In much of the USA
and parts of Europe pyrethroid resistance has already been selected for and
its geographical spread indicates that there is not too high a cost to the
mite in becoming pyrethroid resistant.

However, remove the selection pressure (pyrethroid treatments) and the
susceptible strains will again over time, outnumber the more resistant
individuals. We have seen this in Europe.

Resistant or tolerant genes - whatever you care to call them - will never be
eliminated entirely from a wide area of high infestation but using
treatments with different modes of action the resistance percentage levels
can be kept down low enough to allow acceptable control of the pest.

Low level potential resistance [to any given substance]could be be said to
be present in any population, due to natural variation.

As beekeepers we need to manage it to our advantage.


Max

Dr Max Watkins
Vita (Europe) Limited
21/23 Wote Street
Basingstoke, Hants RG21 7NE  UK

Tel.   +44 (0) 1256 473177
Fax   +44 (0) 1256 473179

http://www.vita-europe.com


-----Original Message-----
From: Informed Discussion of Beekeeping Issues and Bee Biology
[mailto:[log in to unmask]]On Behalf Of Lipscomb, Al
Sent: 23 April 2001 20:11
To: [log in to unmask]
Subject: Re: BEE-L: approval required (E0550CDA)


> > I am struck that no one is suggesting a combination miticide attack.
> > Alternating Apistan and Coumaphos.
>
> I recall that the active ingredients in Apistan and Coumaphos
> are a bad
> combination, and to
> be avoided.  I don't recall the specifics, but details are in
> the archives
> somewhere.

There was some thoughts that it will take N generations of mites
before Apistan will be useful against a mite population that
had become resistant. Rotation would only continue the resistance.