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I have used both the screened and solid bottom boards over the years - over the last few years I have been using the screened having read it helps with hive ventilation and mite reduction. I am wondering if there have been any studies done as to what works best or your own anecdotal evidence that one is superior to the other.
 

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I read the thread title and had to chuckle "Is there a consensus...". I think the consensus is there is never a consensus on anything in beekeeping.:)

SBBs were all the rage for a while but enthusiasm for them seems to have waned a bit. Some never liked them. I have seen hives try to propolize the bottom screen and/or the entire hive entrance which I take as them trying to correct for too much ventilation. IMO I'm sure a few mites drop through the screen, but not enough for any kind of significant control.
 

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Consensus? No way.
Yeah, there is almost no consensus with anything beekeeping.

I like SBB because you can see the debris fall from the hive without opening it and it assures ventilation. If left open during the winter where I am the bees will not raise brood in the bottom medium box so this should be accounted for when setting up the hive for overwintering.
 

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I run screens for Summer, swap to solids for Winter- I don't particularly care to test their cold tolerance at -25 with a stiff wind. Sounds like a pain in the wazoo to swap them, but if you're rotating brood chambers anyway, it's no big deal.
 

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I run screened BB in all my dozen-odd hives. The pull-out board is a quick, non-invasive and easy way to get a read on the hive's mite condition. If I need a more accurate mite number, I can always do an alcohol wash, but usually reading the pull-out board is good enough.

Our high altitude Sun is brutally intense during the peak of Summer in my area, and my hives sit in full sun all day. The extra ventilation the screened BB offers in the July and August is a good thing. Especially because the extra ventilation doesn't come at the expense of exposing the hive to robbing with a wide-open entrance.
 

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staple a piece of window screen to the bottom of your sbb and it will catch and kill a surprising number of SHB larva trying to exit the hive. IPM for hive beetles.

I use both, and I'm absolutely sure that hives with solid bottoms send out more foragers on fair mid winter days.

But I don't even really have a consensus with myself.
 

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A constant flow of air in hot weather through an open screened bottom may work against the bees own efforts at keeping the hive cool via evaporative cooling with water that the foragers collect.

From the USDA Agricultural Research Service ....
Bees store their food and raise their young in the honeycomb nest. Honeycomb is made from beeswax, which is secreted by young worker bees, and fashioned into the familiar honeycomb hexagonal shape. Because bees live in these wax combs, though, they have to keep the nest at a constant temperature, not only to keep the colony from overheating, but also to prevent the wax from melting. [HIGHLIGHT]In hot weather, bees cool the colony much like your swamp or evaporative cooler does - by evaporating off drops of water. Bees collect water and spread it throughout the colony in droplets. Then they fan the air to create an air stream over the water drops, causing the water to evaporate and thus lowering the nest temperatures.[/HIGHLIGHT]

http://www.ars.usda.gov/research/docs.htm?docid=11067&page=7
Evaporative cooling (swamp coolers) are likely to be less effective when they are not working within a relatively closed airspace.

One option to utilize a screened bottom is to use one that has an oil tray below the screen (to kill pest that fall through the screen), but has a solid bottom beneath the oil tray to block airflow.

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The Bee Informed Survey people collected data on the percentages of hives surviving winter using screens vs. solids. Basically, no meaningful difference between them in hive survivability over winter. However, I would like to see more detailed analysis of that data. What I really want to see is an analysis of whether people using solid bottoms vs. screened ones tend to be migratory beekeepers and/or treat their bees. It could be that if commercial beeks who treat also tend to use one type of bottom, then the effect of the type of bottom board is getting lost in the analysis. (Believe it or not, commercial beeks who move their bees and treat reported lower, not higher, overwintering losses.)

As I understand it, screened bottoms got started as a tool to control varroa. Experience and lots of studies show that screened bottoms, standing alone, will not protect a hive from varroa mites. If screened bottoms did have that effect, the varroa issues would have been licked a long time ago.

I have used both, and I don't see all that much difference.

Screens are good for mite counts and being able to close the hive and maintain air. In my experience, queens don't want to lay in the bottom box early in the year with an open screen, which I don't like.

Solids are cheaper, and you need to count mites with a sugar/alcohol wash, although that is a better way probably. You can also use a screen to close up a hive when needed.

I suspect all the "bees need ventilation" talk is off-base. Bees don't want ventilation in a natural hive cavity -- they propolize over the ventilation holes. What I really want to know is whether screened bottoms actually interfere with bees ability to cool the hive with water. Anybody who has ever used a swamp cooler to cool a house knows that it won't work if you keep your windows open. I don't know why it would be any different for bees.

When I need a new bottom board, I've started getting solid ones at this point.
 

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There are always pros and cons when you look at solid against SBB's. As I make my own I find it easier and cheaper to make SBB's. I will also close up the bottoms with coroplast during the winter months and even in the summer if new queens are to be mated in any hive, had too many queens return from mating flights and take up residence under the screen. But they have the advantage of being able to see the results of a mite treatment.
Johno
 

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Anybody who has ever used a swamp cooler to cool a house knows that it won't work if you keep your windows open. I don't know why it would be any different for bees.
I'm not sure I totally agree with this.... Swamp coolers need a source of dry air coming in, and then the cooled air needs a place to escape. If you blow 'swamp cooled' air into a space, it will stop working if that air can't vent out a window or a door. We run one on our garage, blows air in from our sideyard, and we have to crack the garage door an inch or the cooling effect stops working.
 

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I use both, I prefer SBB with the ability to add an oil tray (freeman beetle traps). It's the only thing I've found that really works against SHB. I leave them on year round, and have had 15 degree weather twice this year. Next few days we get 24, 25, 27 for lows, but are highs are usually in the 50s. Last week we had two 70+ high days. Bees take it all in stride.
I've stopped adding hives, now I will continue to add freeman beetle traps till I've got one under every hive.
 

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I have used both the screened and solid bottom boards over the years - over the last few years I have been using the screened having read it helps with hive ventilation and mite reduction. I am wondering if there have been any studies done as to what works best or your own anecdotal evidence that one is superior to the other.
UF put out a study that SBB hives had 14% fewer mites sitting directly beside hives with solid bottom boards. 14% isn't enough to stop mites from killing your hive, but it helps...
No link, I was in a Bee seminary with a UF prof that was discussing raising bees in Florida.
 

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I'm not sure I totally agree with this.... Swamp coolers need a source of dry air coming in, and then the cooled air needs a place to escape. If you blow 'swamp cooled' air into a space, it will stop working if that air can't vent out a window or a door. We run one on our garage, blows air in from our sideyard, and we have to crack the garage door an inch or the cooling effect stops working.
What you are describing is positive pressure ventilation. Firefighters use it to vent a house. Blow a fan on an open front door with the air cone covering at least 90% of the door. Then open one window up stairs or at the other end of the house and within minutes the house will pressurize and you best not be standing in the path of that window. The amount of air moved is amazing and is quadruple the amount of venting using suction. So I imagine SBB would be similar. I would think the amount of air thru the SBB might be too much and hinder proper venting of the hive, in the proper proportion. Just surmising, I don't really know.....

I use both, but I wonder sometimes how much I really do to the mite count or if I am helping the SHB to enter and hide. Not to mention the SHB larvae allowed to exit through the bottom and mature under my hives where I can't get to them. Although my only two hives lost to SHB were in solid boards. But they were weakened by something else first, so I think the bottoms had little to do with it. I am moving back to solids as I build this year and time will tell.
 

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How well the bees are able to ventilate a hive will show up in summer by how many bees you see clustering outside the hive. I think that if you have open mesh bottom boards you see less bearding in summer than with closed bottom boards. The bees will ventilate and maintain the humidity in the brood nest area by forming a shell of bees, and opening and closing the shell around that area, just as they form a cluster shell in winter.
 

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See this study reporting a 14% drop in varroa mites with a screened bottom:

http://www.ent.uga.edu/bees/publications/ABJ.pdf

Note also that they pointed out that the 14% drop was not statistically significant. They also said that there may be a trend in studies that suggest that screened bottoms reduce mite populations to some extent. If you want to incorporate a screened bottom, put it over an oil tray - to kill the mites - with a solid bottom beneath that to control airflow and allow evaporative cooling by the bees.
 

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I had brought this topic up not too long ago in the equipment forum, concerning top entrance hives. From what I understand too much ventilation can be a real problem, and so is not enough ventilation. Both make perfect sense to me- all pest control aside. The bees however, seem to be best suited to regulating minor temperature fluctuations because they do this by nature. So I don't see the point in altering what happens naturally.
However, what about the times when exterior hive temperatures reach extremes and causes stress? I'm probably speaking for the greater majority of small time beeks when I say that we can't possibly babysit our hives 24/7.

Now here is where I go a little crazy on the subject: It seems to me that such a solution could be devised to provide additional ventilation or reduced ventilation as needed, through technology. A smart hive if you will. The simplest method could utilize a bi-metal coil that would open a vent- similar to the old style furnace thermostats. The most complex could range from internal sensors, electronics, and small- low voltage motors to open vents or even something like the heat pipes used to cool CPU's. Want to add heat? Solar and battery combo with a small heating element. Surely no one wants to pay more or do more maintenance that what's necessary, but the technology is there to provide solutions to heating/cooling. The only question is whether it's worth it and I'm sure that this would be climate based.
 

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14% less of anything is significant in my book. Plus, I'm a firm believer that any study older than 10 years old isn't all that valuable- to me anyway. Seems that there should be new studies. Does anyone here keep personal journals that could add to the mix?

Another thought I just had was as to when most of our 'modern' beekeeping knowledge was added. We are talking about knowledge that is well over 100 years old. Think about that for a minute- how many people actually forget that the older hives were made of thicker wood, thus altering a hives insulating capabilities? It could just be that the little bits and pieces that we are overlooking from over many years of history, is causing us issues that don't have to be. :eek:
 
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