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Posted: Sun Jul 06, 2008 6:36 pm Post subject: Don't use Screened Bottoms for ventilation!!
Experimentation of an Anti-Varroa Screened Bottom Board in the Context of Developing an Integrated Pest Management Strategy for Varroa Infested Honeybees in the Province of Quebec
accomplished within the framework of the program: “Appui au développement de l’agriculture et de l’agroalimentaire en region 2000-2003” of the “Ministère de l’Agriculture, des Pêcheries et de l’Alimentaiton du Québec, Canada (Regional district of l’Estrie)
Final Report
by
Jean Pierre Chapleau,
March 2002
translated and revised
March 2003
Validation of the function principle of the anti-varroa bottom board
The principle of the AV bottom board hinges on the hypothesis that some varroa mites are alive when they fall naturally off of adult bees. We wanted to verify the validity of this hypothesis. By sampling six hives for natural mortality during a period of 24 hours, we observed that 16% of fallen varroa mites were alive (figure 11). In his study, C. Webster (4) concluded that the percentage of live fallen varroa mites varied from 39% to 50%. The proportion of living fallen varroa mites seems to vary according to different conditions. The confirmation that a part of the falling varroa mites are still alive validates the principle behind the use of the AV bottom board and explains the positive results obtained during the 2001 trials.
The thermal factor and the anti-varroa bottom board
The important difference in the global results obtained in 2000 (29.2% more varroa mites) and 2001 (37% less varroa mites) for sub group AV suggest a confirmation of the negative thermal influence assumed in the 2000 trials. In 2000, all of the anti-varroa bottom boards were operated with the bottom opened while in 2001, with the exception of the YBO group, the bottom boards were operated with the bottom closed. To our knowledge, this is the only operational factor that was systematically different between the 2000 and 2001 trials. The results strongly suggest a connection between this factor and the negative results obtained with the use of anti-varroa bottom boards during the 2000 trials. We can legitimately assume that the brood cluster temperature was lowered with the use of the opened anti-varroa bottom board. Numerous references can be found in scientific literature confirming that lower temperature conditions enhance the development of varroa populations. Ingemar Fries (12) states: “(…) mite population seems to grow faster in cooler climates than in warmer areas (…) it has been suggested that climatic factors are decisive in determining the mite population growth although the mechanism remains unclear.” We can believe that a longer period of time in the capped brood stage resulting from a lower temperature favors an increase in the reproductive rate of the varroa mite’s population. An increase of time in the capped brood stage enables the young female varroa mites to reach maturity before the bee emerges from its cell. Kraus and Velthuis (14) found that artificially reducing the brood temperature of colonies had the effect of doubling the mite population in comparison with control groups. Their laboratory tests allowed them to determine that 33 C was the optimal temperature for varroa mite reproduction. Kraus and Velthuis (14) suggest that beekeepers adopt practices that aid colonies in maintaining brood temperature at 35 C. The results obtained by Kraus and Velthuis were not available when planning for the 2000 trials as they were published in October of the same year. Reference to the influence of temperature on the rhythm of natural varroa drop can also be found in recent scientific literature. Thomas C. Webster (4) found that this drop is correlated to the average outdoor daytime temperature. J.T. Ambrose (13) also found (2001) that when infested adult bees were exposed to variable temperatures in laboratory conditions, the percentage of varroa mites falling from the bees increased with the elevation of the ambient temperature. Here again we can deduce that the brood chamber temperature should not be lowered. _________________ Admin: Gary, at his own request, is no longer an active member of this forum.
Joined: 19 Oct 2007 Posts: 71 Location: Croatia, Istra
Posted: Sun Jul 06, 2008 9:08 pm Post subject:
Hi, Gary
First time that I read this article, thanks for having posted because it confirms all my work until now.
Quote:
We can legitimately assume that the brood cluster temperature was lowered with the use of the opened anti-varroa bottom board. Numerous references can be found in scientific literature confirming that lower temperature conditions enhance the development of varroa populations.
Confirm, use bottom board (observation drawer) only to monitor the fall of varroa.
Quote:
mite population seems to grow faster in cooler climates than in warmer areas (…) it has been suggested that climatic factors are decisive in determining the mite population growth although the mechanism remains unclear.” We can believe that a longer period of time in the capped brood stage resulting from a lower temperature favors an increase in the reproductive rate of the varroa mite’s population.
Confirm, naturall comb = brood nest temperature to normall, shorter capping time, shorter post capping time, emerged after 19 days,...........etcetera. REGRESSION !!
Quote:
Kraus and Velthuis (14) suggest that beekeepers adopt practices that aid colonies in maintaining brood temperature at 35 C.
How you can aid your colonies to maintain ideal brood temperature 35° C?
Avoid sudden changes in temperature!
Avoid too much insolation!
Insulate your hive from all six side! http://www.biobees.com/forum/viewtopic.php?t=1271
Effect of all this: bees healthy, able to fight pest alone!
My point exactly for posting this article. Or as Phil would say Spot On!
I would like to add. There is an imense amount of information out there in cyber land. You have to be real careful in choosing the opinions you apply to what you are seeing in your hives.
Good examples of reliable information are studies and articles which are published in scientific journals. These articles have gone through a process called peer review. The peer review process removes the authors name and any references to people which could lead to bias. Then the article is submitted to several authorities in the feild and they decide if it is accurate enough to be published.
These articles mostly conduct research with out bias. it is the articles that just report observation and fact which I look for and then I compare them to what I see in my colonies. First I learn something and secondly I gain a better understanding of what is happening and why.
Anybody wishing specific information that is reliable just post the subject and I will scan through the thousands of databases which are available to me through the university I attend. Normally the average person would have to pay for access to these articles I get them for free! _________________ Admin: Gary, at his own request, is no longer an active member of this forum.
Joined: 14 Jun 2007 Posts: 4169 Location: UK, England, S. Devon
Posted: Mon Jul 07, 2008 10:44 am Post subject:
Yes, maintaining the correct temperature is important in our progress towards treatment-free beekeeping.
And we still have to deal with the issue of condensation and ventilation.
There have been several reports on this forum of people without screened bottoms having big problems with condensation inside the hive. I have never had condensation inside a hive with a screened floor and I don't know anyone who has.
So perhaps we are looking for a way to have vented floors with some kind of baffle to prevent draughts (or drafts) that still allows vapour-laden air to escape downwards.
One approach may be to have only a relatively small area of screen - maybe directly below the brood area - with the rest of the floor closed off.
Have there been any studies where they analyzed wild bee hives for temp, humidity, ventilation paths etc? I can easily see how a log or tree will be very well insulated. Not sure about moisture control though. _________________ Greg Hounsell Seldom Fools Apiculture http://sfapiculture.ca
Eastern Ontario's first biodynamic top-bar apiaries
The current belief about moisture in a tree cavity is the soft rotting roof absorbes it and wicks it off JUST like the WARRE QUILT ROOF! _________________ Admin: Gary, at his own request, is no longer an active member of this forum.
If one does not have any gaps between their top bars.. is the thinking that the moisture will be drawn up through them and into the quilted pad to be evapourated out? _________________ Greg Hounsell Seldom Fools Apiculture http://sfapiculture.ca
Eastern Ontario's first biodynamic top-bar apiaries
No you have to pull some of the empty bars in the rear it may require moving a follower board backjust make sure the box/quilt sits right on the TB's I would also prop the rear of the hive a bit to draw the vapor in the direction of the quilt. _________________ Admin: Gary, at his own request, is no longer an active member of this forum.
Joined: 14 Jun 2007 Posts: 4169 Location: UK, England, S. Devon
Posted: Mon Sep 08, 2008 9:51 pm Post subject: ventilation, mesh floors and damp
Varrex - your picture illustrates exactly what I am doing to my hives. However, I live in an area that has cool, damp winters, and I have seen too many hives suffering from mould as a result of condensation and poor ventilation.
I perfectly understand the argument about enabling he bees to maintain a sufficiently high temperature. However, the researchers seem to have missed a rather basic fact: HEAT RISES, or, more precisely, warm air rises. This means that BOTTOM VENTILATION, as long as there is not too much turbulence, HAS NO EFFECT ON THE TEMPERATURE NEAR THE TOP OF THE HIVE where the bees will be. It does, however, allow cooler, damp air that flows slowly down the side walls to drain away, so keeping the hive dry.
If you use top ventilation, you risk having the heat generated by the bees leak away, especially if air can also enter through low level entrances. This is how chimneys work.
If you have no ventilation and high humidity in winter, you WILL get damp problems, including mould growth on stores, which will cause your bees more problems than a few mites.
Therefore, whatever the scientists say, so long as I observe my bees emerging from winter, safe and dry, I shall continue to use bottom ventilation in my hives. If some other arrangement works for you in your area, that's just fine by me: I never tell anyone that they should do this or that if their local conditions dictate otherwise. _________________ Friends of the Bees www.friendsofthebees.org
The Barefoot Beekeeper www.biobees.com
I believe that a comparison to a tree cavity is the way to go AS A START POINT after all bees nest in tree cavities all over the world. Everyone will need to adjust to their own local conditions! I stated the first time I saw a Warre quilt that I thought it was the perfect recreation to the roof of a tree cavity because heat rises. The only way to tell what is going to work is to run a variety of systems side by side and compare results. Remember we are the first to push TBH beekeeping forward! _________________ Admin: Gary, at his own request, is no longer an active member of this forum.
Joined: 14 Jun 2007 Posts: 4169 Location: UK, England, S. Devon
Posted: Tue Sep 09, 2008 4:43 pm Post subject:
Gary wrote:
I believe that a comparison to a tree cavity is the way to go AS A START POINT after all bees nest in tree cavities all over the world.
I suspect that the common factor here is that tree cavities typically have a lot of free space below the combs, especially when compared with framed hives. This is similar in effect to floor-level ventilation, in that it allows an exchange of descending, damp, cool air for 'fresh' air from the entrance.
Clearly, if we had that amount of space (=unheated air) in our hives below the comb, then having sealed floors would be compensated by the volume of air below the bees. I thinl Ian Rumsey incorporated this idea in his vertical hives - and of course it is part of the Warré design.
In short, I think some air circulation below the bees is important: whether this is just empty space or a mesh floor is less so. In dryer climates, it probably does not matter as much. _________________ Friends of the Bees www.friendsofthebees.org
The Barefoot Beekeeper www.biobees.com
That thought had occured to me and I thought about leaving on of my drawer doors open to test it here. I could open it and tack screen over the enreance to keep the critters out. Do you think with a small front opening, a screen under the brood nest and a sloid floor under that with the back door a jar would provide enough? _________________ Admin: Gary, at his own request, is no longer an active member of this forum.
Joined: 14 Jun 2007 Posts: 4169 Location: UK, England, S. Devon
Posted: Tue Sep 09, 2008 10:34 pm Post subject: overwintering and ventilation
Gary wrote:
That thought had occured to me and I thought about leaving on of my drawer doors open to test it here. I could open it and tack screen over the enreance to keep the critters out. Do you think with a small front opening, a screen under the brood nest and a sloid floor under that with the back door a jar would provide enough?
That sounds about right to me.
One day, I hope to have enough hives - and time to look after them - so that I can say: "OK, let's try 10 hives with only screened bottoms, 10 with solid floors, 10 with partially ventilated floors..."
But we have a situation here where there are quite a few TBHers going into winter - many for the first time - not knowing if their bees are going to make it to spring. I have not yet lost a colony in one of my KTBHs and I don't intend to start now - but I may have been lucky. All I can say is that people need to be aware of their local conditions and take note of what successful beekeepers do in their area, and translate that into top bar hive conditions, and chuck in a handful of common sense and elementary physics, and then pay close attention to what actually happens in Beelandia (as the other Gary says) and share the information here, so next year we are all a little older and a little wiser and we can learn from each other's successes as well as mistakes.
So far, in my apiaries, ventilated floors (even no floor at all) seem to have worked well. That may also be the case in similar latitudes, or it may be that in much drier places less ventilation is better, as there may be a greater differential between the inside and outside humidity. Obviously, in latitudes where there is no winter to speak of, things will be different again.
Take notes, my friends, and tell us how you get through the winter - if you have one - and let's hope for a better beekeeping season ahead, as this one - here at least - has been one of the worst in living memory!
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