Varroa-Virus Interaction in Collapsing Honey Bee Colonies

[oliver90owner]

90%?

I would doubt that, in many cases!

RAB

 

[For want of a better word]

"Have noted that colonies with a large drop of mite in Autumnal Apiguard treatment also present a large drop of mites with vaporisation of OA in midwinter, Colonies with very low Autumnal drop have few if any mites dropped with midwinter vaporisation"

obvious really - apiguard is say 90% effective.

two colonies - 100 mites and 1000 mites. drops are 90 & 900. leaving 10 & 100 to reproduce before winter. still a 10 fold difference in numbers at OA time.

A good enough reason then for midwinter VAPORISATION with OA... even if the OA only kills off the overwintering remnants of the Autumnal mites.

I still have doubts on opening up any colonies midwinter to tip a sticky syrup with Oxallic acid haphazardly stirred into it onto them!

 

[itma]

The important thing I noted about this thread is that (properly) treated colonies survive the winter?

Yes, its a rather odd paper.

The colonies (and their treatment) weren't under the control of the experimenters.
The published results run from April to April, but reflect treatments (or not) during the previous autumn. And it would appear that the treated colonies were treated during the April to April period, but that these treatments (and times) were not spelled out. It would appear from the varroa graphs that at least some of the "organic acid" colonies were treated in autumn (with Formic, seemingly) ...

Category A included 11 colonies (A01 to A11) from seven apiaries which were treated using organic acids mostly formic acid and always oxalic acid. Formic acid is used in early autumn followed by oxalic acid in early winter. Category B included nine colonies (B01 to B09) from seven apiaries which were treated using the pyrethroid Flumethrin. The beekeepers use non-standardised treatment methods which result in diverse methods of application and treatment times.

However, it appears that the colonies ONLY got autumn and/or winter treatment -- no other treatment for varroa.



The varroa results are also presented in a form that is unusual to me.
The experimenters were sent samples of about 200 bees.
And they then counted the phoretic mites and expressed their result as mites per hundred bees.

Now, I may be pernickety, but even 2 phoretic mites per hundred bees seems rather a lot to me.
The proportion of mites that are phoretic will vary enormously during the year. In winter, when the colony is broodless, 100% of the mites would be phoretic.
In summer however, we'd expect at least 80% of the mites to be hidden away in the brood cells.
So the real mite population proportion then is more like 10 than 2 mites per hundred bees.
With 50,000 bees in the summer colony, that equates to about 5,000 mites. Or about 5x the UK "Oh Sh!t" threshold.
However, the researchers were reporting June/July/August figures in that range on the treated colonies.
The figures show a jump in the "mites per hundred bees" in September. I venture to suggest that this is simply an increase in the proportion of phoretic mites as brooding reduces at the end of the summer.
I really don't think that scoring the number of phoretic mites per hundred bees gives a true representation of the scale of the varroa problem.
The experimental method has been informed by virology rather than beekeeping!
The phoretic mite count needs further careful processing to correctly indicate the colony infestation level.


Now, I know that the study was supposed to be of viruses in collapsing colonies, but if "treated" colonies were to be used as a baseline for comparison, I think that best-practice responsive treatment rather than haphazard calendar-based treatment ought to have been used as the baseline.
Although the untreated colonies did really badly, the treated colonies really didn't do very well --

Seven colonies (A04, A05, A09, B09, C01, C02, C03) died over winter and were not sampled in April 2012.

So on the measure of survival alone, 0/3 from the untreated group got through, but only 8/11 of the organic acid group survived, while 8/9 survived the winter following pyretheroid treatment.
Which is rather an unfortunate finding - and one which I would suggest was due to calendar-based rather than responsive treatments. (And not what RAB was intending with his comment quoted at the start of this post.)

 

[alanf]

Does UK send any queens or bees to other countries?

Possibly...
many queens are raised in the UK by breeders and small scale beekeepers for their own use ... less than 0.05% are imported which is when you think about it a very small number

From the NBU SE bee inspector report 2012, the officially notified figures for England and Wales:

From the EU – 8267 queens were imported from Austria, Cyprus, Czech Republic, Denmark, Germany, Greece, Italy, Poland, Romania, Slovenia & Spain. Up from last year (4113) the largest importer being Greece at 3630
From 3rd countries (non EU) – 590 queens were imported from Argentina (100) and New Zealand (490). Much reduced on last year’s total of 1762

8857 imported queens in 2012. In the Honey survey 2012, the NBU estimate is 173,000 colonies in the same area. That's enough queen imports to re-queen 5% of colonies in 2012, a lot more than 0.05%.

Of course, not every colony is re-queened every year. Say the average queen lasted two seasons; anyone know any actual statistics in the UK, or introduction success rates? In round numbers that would be 10% of colonies with imported queens, which suggests 90% are bred locally.

Anecdotally, imports increased in 2013 after winter losses. Also anecdotally there are personally imported queens which are not recorded on the system, many from Eastern Europe. To return to the original question, no authority in the UK tries to collect export statistics, as everywhere else they are concerned only with licensing imports. With a later and more uncertain breeding season in the UK than further south, it's unlikely that any of the small scale commercial breeders have a significant export trade. Inevitably there will be a few, trading with friends in France or Ireland perhaps but nothing on a commercial scale.

While some entertain the idea that breeding native "British Bees" is possible, I think the numbers say that anyone open breeding in the bulk of lowland England and Wales is not going to maintain any specific characteristics for long.

 

[Finman]

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Properly treated colonies....

Beeks have treated so long and so much.


But results are variable...it is not only varroa, which kills.

Couple of years ago Switzerland lost 50% of its hives during winter.

Almost same in Canada. What really happened...They say that it was varroa.

There are guys whose winter losses are practically zero.


MOSTLy the losses of varroa are reducing the winter cluster and weak spring build up in weak colony. Then reduction of yield by delayed foraging power.

It need not to be much mites and honey surpluss collapses in the hive.
When mite tolerant bee strain pull off contaminated brood, the reduction of bees is so big that the yield is only 50% that of normal.

Same with chalkbrood. it does not kill but it collapses the yield of the hive.

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