> I always make a point to take all washes from the same general area, which could be the difference.

I have done countless samplings of all types including ether roll, alcohol wash, and sticky boards. The critical variable is obviously: mite load. All other variables we attempt reduce to the number 1. X=1, so nothing changes. \

The significant other variables are numerous and include: where the sample comes from (I always try to get bees off of open brood). Time of day, colony strength, proportion of young to old bees, progress of the mite infestation (this is very important: in the later stages of decline, there may actually be fewer mites, if the mite ridden bees have mostly left the hive).

All these same variables apply to all these techniques, but I think sticky boards are most prone to extraneous variables and that the ether roll is by far the most reliable. BUT, the interpreter has to factor in these other variables and adjust his/her assessment accordingly. 

This is why it is usually best to treat the apiary as a unit. If any hives are going over the threshold, you have a problem that will be best addressed by treating all the hives AS IF they are in the same boat. If you had a field of corn and some cobs had worms, you wouldn't just treat those plants.

On the other hand, if you are trying to evaluate mite resistant in individual colonies, to propagate their traits, you might treat on an individual basis to avoid confounding the affects of quality bees. Then again, you may wish to treat these bees more aggressively to avoid losing them, since no bees are mite proof and you can't propagate dead bees (well, you can using semen but never mind)

PLB

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