> Need some help here, but my understanding of resistance development would 
> make the practice of reduced treatment result in faster resistance 
> development.

I think this is a more complex issue than many would admit, however, my 
understanding of the percentage kill question is that if a pesticide is 
applied so that it blankets the target zone and is used at a concentration 
that kills 99.9999% of the target pest, the 0.0001% that survive are very 
likely to be either mutants which are resistant or individuals which are 
genetically significantly less susceptible to the pesticide than the others.

Of course, at this low survival rate, the odds are very slim, and those 
individuals may well be less fit than the population which lacks that trait, 
and fail to thrive, or they may meet with an accident, fail to reproduce, 
etc. BUT, if they do reproduce, (and they do not need a mate) then the 
resulting population will have a fairly high incidence of the resistant 
trait, and these individuals will eventually meet others with some 
resistance mechanism, and off we go...

On the other hand, if the kill is lower and allows some non-resistant 
individuals to survive each time, then the population is less likely to be 
dominated by resistant types, and they are forced to compete (and mate) with 
the average mite genotype keeping them diluted.

It is a numbers game.  Somewhere between total annihilation and no treatment 
is a the sweet spot for developing resistance.  I am sure that the question 
has been modeled many times, with differing assumptions and inputs, and that 
the result is the recommended doses we are given.

These recommendations, which differ from country to country,  are 
doubtlessly based on assumptions that include risk of operator error, 
average climate, and some ideal cluster size and density, along with optimal 
pricing for maximum company profit taking into consideration the probable 
product life on the market and IRR.

Smart operators have noted, though, for example, that the dose for Apistan 
seemed to assume worst case conditions -- fall application in warm weather 
with bees on the bottom board -- and soon learned that  a big boost in 
efficacy was achieved by using Apistan in spring when the bees were far from 
the bottom board much of the day, and falling mites would perish in the cold 
lower regions.  Add the fact that a larger percentage of the mites were 
necessarily phoretic due to reduced brood rearing at the time, and that the 
mites were old and tired from winter, and it quickly became apparent that 
one strip in such circumstances was superior to four strips in early fall.

FWIW

This just a start on the question, but I am out of time.

I'm sure Bob will add more.

             ***********************************************
The BEE-L mailing list is powered by L-Soft's renowned
LISTSERV(R) list management software.  For more information, go to:
http://www.lsoft.com/LISTSERV-powered.html

Access BEE-L directly at:
http://community.lsoft.com/scripts/wa-LSOFTDONATIONS.exe?A0=BEE-L