I'd like to direct this question about tracheal mites testing to those who are knowledgable about the question of mite testing and treatment - specifically bee scientists and commercial beekeepers: First some background: Last year we found that the 25th bee sampled from the honey house windows had tracheal mite damage. Tests this year, we had exactly the same results. I've gathered samples of about a hundred bees from a number of yards, now and started pulling them apart. I've done about 20 from each of several yards and found nothing. The Problem: I'm wondering how many bees I should do from each yard. We have about 24 hives per yard and I guess the number to look at from each sample depends on the level of infestation that is considered the threshold for requiring treatment. I unfortunately don't know how to do stats (I really should learn), but I do know that if you are looking for - say 20% infestation in 1 of 24 hives that may have lower or no infestation - that there is a function to determine the number to do that would give 95% certainty. can someone help me with this? Some Considerations: The management decision involved here is that there is a cost in testing and there is a cost in treating. The sum of these should ideally be lower than the expected loss resulting from undetected or untreated hives dying in winter. Therefore, testing costs are only worth incurring if there is a a reason to assume some measure of risk exists. However the testing cost is already spent by the time one knows if there is any risk of loss. So at that point, only the costs of treatment (including any loss due to treatment) must be less than the expected costs of not treating. My first run at this assumes that a surviving hive is worth $75 in the spring and that a hive dying of TM is going to consume about $10 worth of feed before succumbing and it will cost $5 to clean up the mess. So if it costs $90 to treat a yard to save only one hive, It is only questionably worthwhile. Here are the questions: 1. At what infestation level in an *individual hive* should one treat in the fall? 2. What sampling level of *each yard* should provide adequate indication of such a need? 3. Is it sufficient to only look for darkening in the trachea when checking (very fast and easy), or is it necessary to look for more subtle signs of mites in bees? Regards Allen W. Allen Dick, Beekeeper VE6CFK Rural Route One, Swalwell, Alberta Canada T0M 1Y0 Honey. Bees, Art, & Futures <http://www.cuug.ab.ca:8001/~dicka>