# Research on Screen Bottomboards



## naturebee (Dec 25, 2004)

"Three years of research at Dyce Laboratory at Cornell University have shown that screen bottom boards have no effect on mite populations [Fig. 11]. The reason for this is unknown, but it may be because the fallen mites are sick or old and no longer able to reproduce. However, research on the efficacy of screen bottom boards is mixed. Two other studies have shown numerical benefits from screen bottom boards, but the advantages were not statistically significant."

http://www.masterbeekeeper.org/B_files/varroa_drone_removal_3.htm


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## BjornBee (Feb 7, 2003)

Joe,
I have seen studies show something from 5 to 17 percent reduction in mites when screen bottoms used. If used properly. (Don't ask for the papers. I have no idea where they are)

I have said all along that even 5% reduction would certainly be beneficial in my efforts. I think the more 5%'s you can achieve the better. Whether it be SBB, foundation choices, apiary location, and other IPM management strategies. I think there are no silver bullets. But 5% here, and 5% there, all adds up.

Personally, I have stated in the past that I hate to see effort and wasted research funds, to tell me something along the lines of what SBB do or don't do. There are bigger issues.

I believe that SBB effectiveness is directly related to the bees hygienic and grooming abilities. Do bees with better grooming behavior benefit more? I don't think I need fancy studies to answer that.

Anyone who uses screen bottom and counts mites on a non-treated basis, certainly can see that mites do fall down to the bottom board. How could there not be an impact or reduction to mite levels knowing mites falling to the ground throuigh a screen would not make it back to the hive. A solid bottom board allows the fallen mites to hop the next bee back up to the cluster.

Yes, I suppose that arguing that mite "age" comes into play. And what type mites fall naturally. Old, dying, etc. Of course its never black and white, and always with gray matter. 

Joe, I know you know most of what I said. Its just comments backing my own management strategies. I have never seen a study or claim of anyone stating that bottom boards somehow handled the mite problem. I have heard many say that it "helps".

I also can say that 5 years has been a long time in breeding efforts. I can say that my bees are different from what I had 5 years ago. What Cornell had in 2002 and prior in regards to bees with hygienic and grooming abilities is long gone.

I'll stick by my 5% and use them just the same. Many things go into making beekeeping work. This is just a small piece of the puzzle.


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## naturebee (Dec 25, 2004)

Mike,
I just thought the research was intresting, thats why I posted it. I'm neither pro or con SBB's. But sometimes, the impression given by some that recomend them is that they are more effective than they acturally are. 
Best Wishes,


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## Robert Brenchley (Apr 23, 2000)

To me, there are two inportant plusses to SBB's. firstly, they reduce damp in hives by improving ventilation. This reduces winter condensation, mould, and chalkbrood. Secondly, they make it much easier to monitor what's going on inside the hive. Not only can I estimate mite levels and look for damaged mites without disturbing the bees, I can tell whereabouts a winter cluster is, get an estimate of its size, and I can tell when they're chewing out capped cells, since this results in white bee bits appearing under the screen. Wax moths breed in the debris, and I can monitor for the reappearance of Greater Wax Moth quite easily. All this makes the things more than worthwhile.


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## BjornBee (Feb 7, 2003)

Joe I agree.

From the research you stated:

"Many studies have shown that mites fall off of bees at relatively high rates, even when no chemical treatment is present. Many of these mites are still alive and manage to reacquire a host. It is commonly believed that mite populations can be suppressed if these fallen mites can be removed from the colony before they reacquire a host. The screen bottom board allows mites that fall from bees to fall out of the hive. Since they cannot re-enter the hive, they cannot reacquire a host and they cannot contribute to the growth of the mite population.

Three years of research at Dyce Laboratory at Cornell University have shown that screen bottom boards have no effect on mite populations [Fig. 11]. The reason for this is unknown, but it may be because the fallen mites are sick or old and no longer able to reproduce. However, research on the efficacy of screen bottom boards is mixed. Two other studies have shown numerical benefits from screen bottom boards, but the advantages were not statistically significant. One study has demonstrated a small but statistically significant benefit. Screen bottom boards do not appear to damage colonies. If effective mite knockdown agents can be identified, screen bottom boards may play a more significant role in mite management."
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The thing to note is the last sentence. They themselves suggest that if a "knockdown agent" can be identified, then the impact could be more significant. I have stated many times about grooming "triggers", such as crisco, menthol, thymol, smoke agents, etc., all being beneficial to enhancing grooming and hygienic behavior. I also will state that certain bees are hygienic and groom better than others.

This study to me on the surface discounts the value of SBB. But if I read between the lines, they are actually mentioning other studies that have shown positive impacts from SBB. And they also suggest that the use of SBB could be more effective than what they found themselves.

I am only stating this as I have seen this study mentioned numerous times previously, in some way attempting to discount SBB's. The study does not do this. IT leaves much in the gray and really settles little while leaving doubt and questions about their effectiveness.

With all that said, I agree Joe that the real impact needs to be within reason. Wild claims and statements taken out of context are rampant within the bee industry. SBB are but a small piece of the puzzle.


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## BjornBee (Feb 7, 2003)

RB, I totally agree. But my posts are already too long. I thought of going in that direction but wanted to keep the suffering from the length of my post to a minimum...


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