Varroa treatment

[gavin]

That was an interesting report Jimbo. In the introduction the finger was also being pointed at spring formic treatments having a very detrimental effect on drone production. I wonder if this could have worsened Eric's winter losses given that he's an enthusiast for formic acid treatment, or may even be the cause of Grizzly's drone-free colony he mentioned a while ago? From that report:

'Results of their study were discouraging. Colonies treated with formic acid removed most
of the drone eggs from combs and delayed much of the colony’s drone production. In
addition, treated colonies produced less than half as many drones as untreated colonies
(means of 1549 vs. 3800 drones, respectfully) and adult drone longevity was reduced.
Similarly, Westcott and Winston (1999) discovered that colonies treated with formic acid
had reduced brood areas compared to control colonies, which could potentially reduce
colony strength. The amount of honey produced by colonies can also be affected by
formic acid, depending on the formulation. Skinner et al. (2001) tested two formulations
of 65% formic acid: a gel, and the other with formic acid absorbed into a fibreboard pad.
Colonies exposed to formic acid in the fibreboard pad stored less honey than both control
colonies and colonies treated with the formic acid gel formulation.'

[Jon]

I raise queens and use thymol as my only treatment, I have used oxalic once and only once I had more q/less or drone layers the following spring than I have ever had,

Hi Kev.
In defence of Oxalic acid, I used it for the first time (trickled in sugar solution) last December as a follow up to Apiguard in September.
All my colonies came through winter and only one nuc was missing a queen.
I still have most of my 2009 queens and none has turned into a drone layer.
Several 2010 queens turned drone layer within weeks and these had never had a whiff of Oxalic acid.
I think you have to be careful re. cause and effect as there are multiple factors behind queen mating problems.

I reckon the Apiguard/Oxalic acid combination is one of the softest varroa treatments available

[beebreeder]

Hi Jon
Its a personal thing I think, I am not the only queen rearer in this part of the world feeling the same, I have read a report on the web on the effects of oxalic on queens and will try and dig it out and put the link up, then like me you can make your own mind up. How did your queen rearing go this year?
regards
kev

[Neils]

It will be interesting to se if they still have bees in April.

My suspicion is that (excluding other influences) yes, they'll have bees come April. How well they get on from that point remains to be seen. going to stick this in caps lest anyone misunderstand me: AS A RELATIVELY NEW BEEKEEPER I'm starting to view Varroa as a more "long term" problem. I'm starting to think that you could stop treating at all tomorrow and you'd have bees come the spring, you might get away with not treating at all next year too but after that, unless you're really lucky, you're going to be keeping, at best, some very poorly looking bees. I think this is why you see, certainly in some circles, lots of proclamations of "varroa free" bees that suddenly go very quiet after a couple of seasons.

I raise queens and use thymol as my only treatment, I have used oxalic once and only once I had more q/less or drone layers the following spring than I have ever had, I have not used it since and things are back to normal, I know Pyretheroids seem to make drones dry! and obviously unless we are making our own f/dation or using Top bar hives!!!! then all the foundation by now has some residues in, but having said that this has been one of the best summers in years for queen rearing down south, how has it been in Scotland.

You can always stop using foundation. My supers are all foundation-less and I started a couple of 14x12 brood frames without foundation for, amongst other reasons, the crap that is in the stuff, next season will be the acid test as to whether I can properly manage multiple hives without using foundation in the frames.

[Jon]

How did your queen rearing go this year?
regards
kev

I hatched over 100 grafted from my two best colonies and I divvied them up between friends and members of my BKA
I reckon about 60 were mated properly.
I kept about 25 for requeening and for making nucs but I have been combining nucs lately.
To keep the thread on topic, I think I should have treated the nucs for varroa at the end of July rather than the start of September as many of them have been building up more slowly than expected and I have seen a few bees with deformed wings on the combs.

I'm starting to view Varroa as a more "long term" problem. I'm starting to think that you could stop treating at all tomorrow and you'd have bees come the spring, you might get away with not treating at all next year too but after that, unless you're really lucky, you're going to be keeping, at best, some very poorly looking bees.

Hi Nellie
If the varroa infestation is too high they wont even overwinter as there will be no healthy longer lived winter bees raised in the Autumn.
I have been pointing out for ages to the natural beekeeping people that you would need to keep a colony for 3 years without treatment to demonstrate that it can coexist with varroa.
Swarming seems to be encouraged and this is one way of ditching 80% of the mites which are left behind under the cappings.
It is a system which selects for swarminess which is not a very desirable trait in beekeeping.

The other thing is to understand the arithmetic. At certain times of the year, mites are no problem but when brood rearing drops off in late summer the mites destroy too many pupae.

I posted this a couple of weeks ago on the bbka site.

Take a total varroa population of 400 mites in July which would not be that unusual in my colonies.
80% will be in the sealed brood, ie 320 mites.
In July the brood nest is huge, even in my native type colonies it can be over 30,000 eggs, larvae and pupae. Others may have a brood nest double that size.
If I make another assumption that the queen lays at the same rate every day, capped brood will be about 60% of the total brood area so the 320 mites will be distributed among 30,000 * 0.6 = 18,000 cells. This amounts to 1.8% of cells affected.
In addition it is known that varroa mites are 12 times more likely to be found in drone brood and there is usually lots of drone brood in a colony in July so the percentage of worker brood affected is probably much less than 1.8%

In September the calculations change quite a bit.
The queen is laying less and the brood nest is often down to 10,000 or so.
The varroa population is now 1600 of which 80%, 1280 are under cappings. There is little or no drone brood present.
The varroa now affects 10,000 * 0.6 = 6000 cells ie 21% of the brood affected. (assuming 1 mite per cell rather than multiple occupancy)

If you start with 1000 mites in July the percentage of brood affected is 4.4% in July but rises to 53.3% in September based on these assumptions.

[GRIZZLY]

As mentioned elsewhere, my drone free colony was only treated with Apistan-so no formic acid interference with the drones