Hi Everyone,

Jim wrote in part:

"b)  So, if you detected 3 mites, and assume that this is 100% of "mites on bees",
     you may have 3 mites "in cells", and may soon have 10 to 15 mites (male mites
     die after mating, so you never would get a full 6 mite increase from every mating).
     From there, the numbers start to get scary, not matter what ratio of male to female
     mites you assume out of each "generation".  Even a minimal "powers of 3" (where
     3 reproducing offspring per female are created) rate leads to:

        3, 9, 27, 81, 243, 729, 2187, 6561, 19683, 59049, 177147 "

Hold on there Jim, take a look at the published research on varroa reproduction.  The real numbers are considerably less than 3 daughter mites per mother per brood cycle.  The most published numbers are in the 1.6 - 1.3 range which frankly is a pretty low reproductive rate for a mite.  Now the varroa generation time is the length of a capped brood cycle or about 10 to 12 days so you will get a better idea of the population growth using 1.5 as the mulitplyer and 10 days as the generation time.  This still will result in mite populations growing to damaging levels more quickly then you might think.  Research also tells that more of the mites are in the brood than are on the bees at any given time if brood is present so a 3 mite drop is the result of more than 6 mites.  A guess would be at least twice as many mites in the brood as on the bees.  Here is an example starting with just 10 mites:
10, 15, 23,35, 53, 80, .....  this is for only 6 mite reproduction cycles or about 60 days.  If you are looking at mite populations considerably higher which is usually the case here the mite population over the active bee season can get pretty impressive and the impact on the colony equally impressive.  My point is Tom, don't panic about finding a few mites now but you do need to keep tabs on what is happening in your colonies and be ready to take measures to reduce the varroa population as it builds toward damaging levels.  The real wildcard here is that you don't have any idea of the mite invasion rate ( number of varroa being brought into the hives from outside ) which can very quickly increase that population in the hive toward damaging levels.
The good news is you found them early so have time to monitor levels and prepare for needed treatments and begin to learn about managing varroa in your colonies.

Good luck.  Beekeeping will survive varroa.

blane




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Blane White
MN Dept of Agriculture
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