On Mon, 2 Jun 2003 04:59:44 -0500, Bob Harrison <
[log in to unmask]> wrote:

>When you add the word (yet) I  believe in your mind you would not be shocked
>to find scientific  evidence to prove that the coumaphos resistant varroa
>now found in Florida  and New Jersey are in fact resistant to all three of
>these chemicals coumaphos, fluvalinate and amatraz.

I would not be shocked, but perhaps intrigued because if the mites are indeed
doing that it means three possibilities:

1). the mites were exposed to all three chemicals and have built resitance
sequentially (i.e. to fluvalinate first, then to amitraz, then to coumaphos).
I.e. someone has been using amitraz perhaps illegally.

2). the mechanism of resistance is increased detoxification and resitance to
one enabled the mites to be resistant to others. This can be verified through
biochemical study (no live mites are need for biochemical study, however to
verify that they are resistant to all three in a lab study, indeed requires
live mites. often field assays are not good enough for publication purpose).

3). mites developed resistance to fluvalinate, but developed resistance
quickly to other chemicals (Llyod's point). This is also possible. In the cas
of calorado patato beetles, the current life span of chemial control (before
resistance takes over) is about 2-3 years, while in the 50s, it took over 10
years. This seem to sugget that once a bug acquires some arsenal for
resistance, it can shuffle (re-arange) the genes and fight a new drug easier
(usually because of mechanism 1 and 2 of my previous post). cross resistance
based on target site alternation would depend on how closely related the
chemials are, and on the surface, gene suffling should not help. but who
knows.

>If scientific research says those varroa should have reached the LD 50 and
>did not then is the problem in the application?

Field assay should always be followed by lab assay to verify that mites are
indeed resistance to various chemicals.

>
>As a small orchard owner I realized years ago that timing and method of
>application was as important as the chemical used.
>
>Bob
>

Zachary Huang
over 300 beephotos at http://photo.bees.net

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