> I noticed in various experiment, that when
> reaching 1 varroa/100bees the curve was
> already in the exponential phase
If only sampling 300 bees from a colony of 60,000-plus, your odds of even seeing the initial varroa that would prompt one to prudently treat "when the curve still looks flat" are vanishingly low.
This highlights the superior nature of sticky boards - they allow the entire colony to be the "sample", and make immature white mites an additional signal for "reproduction". When the "threshold" is single-digit mites per 300 bees, it is (statistically) evident that a more sensitive/thorough test is required.
Inserting a sticky board, coming back in 3 days, and scraping the board contents into a tub of ethanol ("denatured alcohol") to count what floats is just as quick in terms of time spent per colony as a sugar shake or ether wash, and gives one a far better chance of catching varroa early, because the first hive in a yard to show varroa is a good clue that the whole yard needs treatment. Better yet, it can be done at night, so it takes no time away from scheduled daytime hive work.
Nearly everyone's moved away from sticky boards in recent years, but nothing helps a "screening" process like increasing the size of the sample, and a sample size of 100% is hard to beat.
I've said this repeatedly - the entire concept of a "treatment threshold" is inherently statistically invalid when based upon such small samples. When there is little difference between the lowest "level of detection" and the "treatment threshold", you need a better test. But beekeeper have arm-twisted the extension and research communities into only thinking about "quick and easy" testing and "one yard-visit" approaches, which is part of the reason why varroa has persisted despite so much effort to find a control worthy of the name. And the basic concept of "testing, then treating" has been supplanted in many cases by regular proactive Oxalic fumigation, an approach that is hard to argue with in fall, when any colony could rob out a collapsing one.
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