Colony Temperature & Humidity

[pargyle]

I've been monitoring (in a very low tech way) the temperature and the relative humidity (RH) in my hive immediately above the frames. My hive (although not as thermally efficient as DerekM's) is very well insulated with a sandwich construction that is 30mm timber/40mm HD Poly/15mm timber.

The temperatures inside the hive have rarely fallen below about 21 degree C and have been as high as 31 degrees. The RH has been up to 85% at times and even now, when the majority of stores have been capped, varies between 61% and 72% dependent upon the colony temperature - which, of course, is lower in the morning and higher in the afternoon.

I have no measurable varroa within my hive (Sugar rolls, alcohol wash, permanent sticky board and visual inspection via the feeder and the clear crown board have not yielded any evidence of varroa). There are no ants or earwigs removing debris either ...

I found this paper which, whilst old research, indicates that varroa breeding patterns are affected by a combination of temperature and humidity.

http://igitur-archive.library.uu.nl/bio/2002-0125-093525/70840217.pdf

Whilst the levels of HR and Temp in my hive are not sufficient to kill varroa is it possible that they are sufficiently high to discourage them ?

There is another thread about whether it is necessary to insulate hives in winter but my question is should we be insulating our hives all the year round - not to give the bees a warmer home but to give Varroa mites a less attractive environment in which they are less likely to thrive ?

Giving the bees the opportunity to raise colony temperatures in the summer to a level where (at peak varroa breeding time) they are going to be detrimental to the growth of the mite population.

Should we all be taking a more active interest in colony temperature and relative humidity levels ?

 

[drstitson]

NO.

a box full of living organisms will be hot and humid.
varroa are adapted to living in normal colonies.

 

[itma]

While I would have anticipated that the humidity inside a sealed brood cell would be pretty constant, that paper is recording statistically significant results in varroa reproduction rate with varying humidity OUTSIDE the cell.
Which is odd and interesting.

But I'm not sure that either
- it offers viable varroa control
or
- that prolonged 80% humidity would be healthy conditions for bees. Its ideal for moulds and fungus - likely including Nosema.

 

[user 6228]

YES
Read the paper...

 

[itma]

YES
Read the paper...

Derek, as the paper states that it is only in tropical conditions when the bees are unable to reduce the RH that this effect will be seen in real colonies, I don't see how this can represent a viable varroa control scheme for the UK.
The problem is that the bees hygrostat is set much lower (probably to maintain mould control) than the humidity required to inhibit varroa reproduction.
The paper explains the unexpected observation of varroa not being such a significant problem in climates that are simultaneously hot and humid.

If you were to just artificially humidify the brood chamber, the bees would be expending lots and lots of energy constantly trying to fan to drop the humidity.
It'd be worse than putting them in an uninsulated hive!
And you'd need to keep up that humidity for months rather than weeks as you waited for the existing varroa to die off.

The paper's experiments were conducted in a temperature and humidity controlled incubator.
The researchers decided not to try and overcome the bees "automatic climate control".
Maybe after another couple of hundred years of global warming, the ambient temperature and humidity in the UK might be so high that varroa wasn't a problem. But instead there would be many other problems ...

 

[pargyle]

But ... it's interesting that the paper states that RH along with temperature has an effect on Varroa ... whilst it is unlikely that hive temp and RH in the UK is likely to reach the levels in the study where varroa reproduction could (almost) be eliminated is it possible that a well insulated hive could reach temp and RH levels that AFFECT ... or hopefully reduce ability of varroa to reproduce ? Obviously, you would not want a situation where other problems (such as Nosema/Mould etc) could be created but is there a balance that can be established using optimum levels of insulation. I suspect that Derek's more scientific approach may, in time, answer some of these questions ?

 

[user 6228]

Derek, as the paper states that it is only in tropical conditions when the bees are unable to reduce the RH that this effect will be seen in real colonies, I don't see how this can represent a viable varroa control scheme for the UK.
The problem is that the bees hygrostat is set much lower (probably to maintain mould control) than the humidity required to inhibit varroa reproduction.
The paper explains the unexpected observation of varroa not being such a significant problem in climates that are simultaneously hot and humid.

If you were to just artificially humidify the brood chamber, the bees would be expending lots and lots of energy constantly trying to fan to drop the humidity.
It'd be worse than putting them in an uninsulated hive!
And you'd need to keep up that humidity for months rather than weeks as you waited for the existing varroa to die off.

The paper's experiments were conducted in a temperature and humidity controlled incubator.
The researchers decided not to try and overcome the bees "automatic climate control".
Maybe after another couple of hundred years of global warming, the ambient temperature and humidity in the UK might be so high that varroa wasn't a problem. But instead there would be many other problems ...

This where you have to look closely at "norms" it refers to and look at other research . Be aware most research is in fixed conditions or refers to stanDard wooden hives. Other research shows bees preferring 75% humidity.... Temperature and humidity are linked. The only real way to find out is to experiment.

High heat losses or high heat gains can lead to depressed RH. This because you get increased internal air temperature differentials which lead to increased convective circulation which then dries out the air by either condensation or temp reduced RH.

Higher levels of insulation reduces internal convective circulation

Put the bees back in control and observe.

 

[user 6228]

Other research shows that not only do bees prefer 75% RH they survive better at that humidity...

 

[Finman]

.
When you look the reseach, it is old 1997. If it would have something usefull in beekeeping it would be adapted in beekeeping.

16 y old... UK has nopt yet adapted even best knowledge about mite treatment, which is 10 y old.

"The present data provide a simple explanation
for the fact that often in tropical
climates population growth of V.
jacobsoni is unexpectedly low."

BUT

The truth is that in tropical climate varroa control is extremely difficult because there is no brood brake (NZ, South Africa, Argentina, Florida)
.
Bees keep brood area in steady conditions, what ever the out temp is.

Number of brood cycles is very essential. Mite population douples itsef in a month. If your hives have brood 6 months or 10 months, it is very different situation in mite population. The warmer the climate, yte more brood cycles.

 

[Finman]

.
Meaning of brood cycles in different climates:

2 cases.

- Brood exists from Feb to November
- from April to Sept (Finland)

Feb ………… June ………… Sept ………… Novem
100………… 1 600………… 13 000………… 50 000 (in theory, in practice dead)

April………… June………… Sept…………
100 ………… 400 ………… 3 200 ………… break...... in winter mites will reduced at the same ratio as bees

However, mite kills hives what ever the climate is or what is temperature or air moisture

.

 

[Finman]

Put the bees back in control and observe.

And hasta La Vista to University Researches!
.

 

[user 6228]

bees prefer to be kept at 75% RH
maximum worker bee survival at 75%RH

go read the scientific literature on temperature and humidity for Nosema and chalkbrood... Humidity is only significant at low temperature.

 

[user 6228]

.
Meaning of brood cycles in different climates:


However, mite kills hives what ever the climate is or what is temperature or air moisture

.

No

 

[Finman]

You should know what varroa does in Britain and in your own yards.
You need not TO know what it does in jungle.

At least I know. I have had varroa 30 years

 

[Finman]

bees prefer to be kept at 75% RH
maximum worker bee survival at 75%RH

go read the scientific literature on temperature and humidity for Nosema and chalkbrood... Humidity is only significant at low temperature.

Good heavens what carbage...When you have a hammer in your hand, all problems look like nails.

- Chalkbrood is a spring disease. And the main reason is that larvae catch cold. It is larva disease.

- Nosema is a disease on late autumn and winter. It vanishes in spring. It is a gut disease of adult bee.

- Varroa has no seasonal cycles. It has variations, what really happens duting summer compared to expected, but it has nothing to do wit nosema or chalkbrood.

And when you look a Brittish weather. It is never proper. It is too humid or too dry but never proper ---for what? Of course top bees!!!!

That research is allready old. If it could have some usefull applications to control mites, it would be surely a standard. But it is not.

Like small cells. It was insisted 10 years that small cell kills mites, but now we know that it does not.

Mesh floor was said too, that it kills mites... but does it?
.
.

 

[Finman]

-
Report 2012 about varroa and humidity.
Since 1997 that kind of researches have been done ....vain job, I suppose

http://www.extension.org/pages/65450/varroa-mite-reproductive-biology#.UmZwTFPyVjo

D. Effect of Humidity

Kraus and Velthuis (1997) wondered why varroa mites were not as big a problem in the tropics (besides that fact that most bees were African), and tested in the laboratory to see if high relative humidity would inhibit mite reproduction. They artificially transferred single mites into newly capped cells, and then kept the brood in an incubator. When relative humidity (RH) was set at 59–68%, on average, 53% of the mites produced offspring (N=174 mites); under 79–85% RH, only 2% (N = 127) of the mites reproduced. The difference in mite fertility was highly significant.

My postdoctor recently incorrectly set the incubator at a RH of 75% (instead of 50%), and very few mites reproduced as a result. If there are ways to artificially increase the hive RH to about 80%, then the varroa mite population will never increase to a damaging level.