Varroa douple itself about in month. How importan it is to stop reproduction?
In winter after brooding season it is idea to slow down the mite population that it has no time to become a harm in late summer for winter bee rearing.
In late summer mites concentrate into last brood which ought to be winter bees.
Lets calculate how the population grows
20 .... 40 .... 80 .... 160 .... 320 .... 640 .... 1280 / September
Marsh...
5 .... 10 .... 20 .... 40 .... 80 .... 160 .... 320
100 .... 200 .... 400 .... 800 1600 3200 . 6400 /Sept
1000 mites is a limit of bad contamination
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Do I need to kill them
After treating I may have 5 mites in spring and 300 in next Autumn. Do I need them. Nothing bad has happened.
Let's suppose that during winter 320 mites has dropped to 100. Next September I will have 6 000 mites.
Lets treat them with efficacy 98%. What means 2%?
3200 ...> 64.. ... ... next August 2000 .. Sept 4000 ...Oct 8000
640 ...> 13.. ... ... next Sept 800 .. Oct 1600
160 ...> 3 .. ... .. next Oct 400
WHAT I TELL: TREAT MITES EVERY YEAR!
If you do not see mites with mere eyes in young bees, you may have 300-500 mites in the hive.
If you see them several with mere eyes, the count may bee about 1000. It needs late summer treatment before winter bees rearing.
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