Hi Kerry and greetings to Malcom Roe,
 
If I can offer twopenn'orth on this topic
 
>    There appears to be a great difference in concentration of active
>   ingredient in the products available, however.
>   Bayvarol has a much smaller concentration of flumethrin (a few (3?)
>   milligrams per strip, anyone have a label handy?) than Apistan hive
>   strips, which are labelled as 10 % fluvalinate. (1 strip is 6 grams. 10
>   % fluvalinate = 600 mg/strip). Unless a different method of expressing
>   concentration has been used, it looks like flumethrin is active at less
>   than 1/100 of the concentration of fluvalinate. Any speculations on the
>   implications of this difference?
 
I've not seen the LD50's for the two products but there is a general trend to use
less & less of more active chemicals. 34 mg active per strip is my memory of
Bayvarol. Can't find the figure when I want it.
 
>   By the way, Malcolm, are 4 Bayvarol strips the recommended treatment for
>   1 hive? (a normal-sized colony, in ____ (fall?)).
>   Is fall treatment recommended? is spring treatment an alternative?
 
Yes 4 strips.
fall treatment, we are geting reports of reinfestation, which may necessitate spring
treatment.
 
>   Is there concern or a tendency for people to re-use the Bayvarol strips?
>
yes! The main complaint I get at meetings is the high cost of 'Bayvarol'
 
Talking to my colleague Daryl Wright, he said that in Canada they had found spring
treatment more effective, possibly because distribution was better since the hive
was more active. Though I would expect that wintering with a high load of Varroa
would cause problems.
 
yours
 
Ian
 
[log in to unmask]  - Northern Regional Bee Inspector, UK -  Bee Curious
phone/fax 01704 822831
snailmail 'Asland' Flash Lane, Rufford, Ormskirk, Lancs, L40 1SW  - UK.