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Bee Hive building & a place to share howto's on equipment
 #9831  by NigelP
 21 Jan 2021, 08:31
Yup, as a general rule drop counts are not great for estimating total varroa numbers. However, the one thing they can't disguise is if you have a large number of mites dropping you need to treat.
Regardless of time of year.
Not sure where the only treat in autumn advice comes from Alfred, but it's wrong.
 #9833  by AdamD
 21 Jan 2021, 11:17
A late summer treatment when the varroa numbers would otherwise continue to increase and when bee brooding is reducing is a good way to rid the colony of most of the mites to prepare it for winter and give the colony the help just when it's needed. I say 'late summer' rather than autumn as if we wait until September/October it can be too late; I believe it takes a couple of brood cycles for the bees to rid themselves of the viruses vectored by the varroa.
I treat in winter too and some colonies - despite being treated a few months before - occasionally exhibit high mite drops. Sometimes the treatments don't seem to work - or maybe robbing has resulted in mites transferring from one hive to another. If we consider that mites double every month (not quite right but a good rule of thumb), it's easy to see that a few mites in December can increase exponentially to a frightening number a few months later. (We are all used to exponential growth now after looking at coronavirus stastics over the past year).

Forum reports of 'surprised beekeepers' have been seen in the past where there has been no apparent sign of a varroa infestation and then, bang, the mite drop is huge after treatment.
 #9835  by Alfred
 21 Jan 2021, 17:36
NigelP wrote: Not sure where the only treat in autumn advice comes from Alfred, but it's wrong.
From the (presumably 'ex')forum guru...
Glad that's sorted-floors will have trays
 #9836  by AdamD
 22 Jan 2021, 09:02
I had a look at the 'Managing Varroa' book from Beebase and that suggests a late summer/autumn treatment and that you might need to treat in the spring if the colony has a high varroa load.
(I did notice reference to the "Cascade Principle" relating to EU treatments - I guess the book need to be re-printed now).
 #9840  by MickBBKA
 23 Jan 2021, 10:08
If they have a high load in spring then you are way behind the curve imho. I think treating in autumn and winter is better to give them the best start in spring. Also you don't want chemical residues in your spring honey ;)
 #9846  by NigelP
 23 Jan 2021, 18:49
Indeed, but if by mischance/mistake you still have a high load come spring....you need to treat. Or any other time come to think of it.
It's nice to be on top of it come autumn, but mistakes happen. I have one hive in the garden, that despite 4 amitraz strips in autumn, is still dropping more varroa than I like to see.
Does this mark me as a failure as a beekeeper or merely human :)
 #9848  by Steve 1972
 23 Jan 2021, 19:09
Failure ...put me first on your list when you start selling those big colonies.. :D
 #9888  by Alfred
 27 Jan 2021, 20:39
NigelP wrote:
23 Jan 2021, 18:49
Indeed, but if by mischance/mistake you still have a high load come spring....you need to treat. Or any other time come to think of it.
It's nice to be on top of it come autumn, but mistakes happen. I have one hive in the garden, that despite 4 amitraz strips in autumn, is still dropping more varroa than I like to see.
Does this mark me as a failure as a beekeeper or merely human :)
I'd say it's confirmation that you've previously been right to subliminate :)