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So, I have both screened and solid bottom boards in my 6 hives.

This year I'd like to go to completely screened bottom boards.

I think I have it figured out to modify the solid boards into screened BB. My 2 questions for the more experienced keepers out there:

1-Can I use a smaller screen than the #8 stuff that is standard? I have a ton of it in my cellar and I'd like to not have to buy if I don't have to. I was just thinking that the mites might not fall through.

2- Anyone see why this might be a bad idea if I can have a structurally sound BB after the modification?

Thanks for the advice
 

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If your goal is to have varroa mites fall thru the screen, 'window' type screening might be a problem. This site suggests common screening has mesh sizes of 1mm, 1.2 mm×1.2mm, 1mm×1.5mm:
http://www.petscreenmesh.com/petscreen/fiberglass-insect-screen-with-pvc-coated.html

but varroa are big enough that some might not fit thru the screen:
The female mite is brown to reddish brown in color, measuring 1.1 to 1.2 mm in length and 1.5 to 1.6 mm in width (about the size of a pinhead).


https://agdev.anr.udel.edu/maarec/wp-content/uploads/2010/03/Varroa_Mites_PMP2.pdf
Could be a tight fit! :eek: :D
 

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If all you are after is ventilation then smaller mesh screen is fine. You just have to clean it as you would a solid bottom board. But if you are.going for SHB control then like Radar Sidetrack said, it is too small.
 

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Is your aim to add a) high level of ventilation year-round, b) monitor mite fall, or c) reduce mite populations in the hive?

These are somewhat different goals, with somewhat different critical paremeters, I think.

I run both screen and solid boards, together and year-round. Mine are optimized for my primary goal which is having a way to do mite counts, very frequently, and year-round. Note that I am north of Albany, NY, so yes, that means I do them in the winter, too. (Just for my own curiosity since there are no published thresholds for treatment during the winter.)

For simple ventilation, wire (not plastic) window screening would work, I think. I must say, however, that even though I read that some people do use SBB in the frigid North in the winter, it chills my bones just to think of it. I keep quilt boxes on top to provide for excellent moisture management so even with a solid BB, I wrap shipping foam sheets around the closure of the monitor slot to seal it up from the cold drafts. But if you're OK with that (keeping a hive at CT ambient winter temps), then window screen would work. It will get gummed up with all the hive debris pretty quickly, and scraping that stuff off will just mash it into the tiny pores, plugging it up like kitchen sieve, I think.

For varroa monitoring purposes you will need to have the floor material be similar to #8 to allow the wretched beasts to fall on through. Otherwise I think it would be impossible to assumme the treatment thresholds are valid because some would escape being counted. And the slot that allows the tray or board to be inserted must be closed off from access by other bees to preserve the mite sample.

For varroa suppression purposes (something that I see mentioned occasionally, but that I don't think works well, at least based on what I saw during my nearly-constant counts last summer), you'd defintely need something that allowed the mites to fall out of the hive en masse and a way for the bees to be prevented from casually re-encountering them outside the hive which might allow them to hitchhike their way back inside for a second chance.

The other issue I have with plain (no solid BB below) screened BB is that last summer during robbing season I observed some bee-felons occasionally sneaked in past a mis-inserted wooden closure thingy and tried to get into the hive from under the screened floor. This really upset the bees inside and seemed to me to be a decent chance for additional mites to be brought in by the robbers to transfer directly into my hives.

As for SHB, I can't see why you'd want any of their larvae to fall out on to the soil so they could pupate. I don't have a big issue with them, but when there is a small increase I found that a twice-a-day pulling of the boards captures enough larvae clinging to it (and which I then squash) that it quickly brings things back into control.

Maybe there's something bad that I'm not seeing about running both boards at the same time, but if you already have both of them why abandon a good solution and carve up your solid boards?

Enj.
 

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I would not cut up the solid bottom boards. You can use them for covers and temporary splits or moving bees.

I make my SBB's out of 3/4 exterior plywood and two 2 x 3's. That give you the extra height that you need to make the boards work.

Just saw a groove in the 2x3 3/4 inch down and glue and screw into the plywood. Cut the hole out in the plywood and cover it with 1/8 cloth. I paint it up before stapling the screen on.
 

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Don't cut up bottom boards.

I build SBB bottom boards using (mostly) offcut scrap.
My design is built of two sub-assemblies that sandwich together, making a strong 2x side rail.
The common design uses a rabbeted 1x on edge. This warps and cups quickly due to the weak rabbets.

I have used "dog-proof" window screeen. This is coarse, tough window screen designed for sliding doors. It doesn't let mites fall through very well. SBB short-circuit ventilation with bottom entrances. SBB are mostly useless for mite-suppression. They are good for monitoring hive conditions, including detecting which frame the queen is on. I have returned to using 1/8" Hardware cloth.

I think SBB (in non-Small Hive Beetle regions) were a fad, whose utility has been tested and mostly found wanting. I still run some, but expect them to serve as monitoring, rather than control devices. I cannot speak to SHB, because my region is not bothered with these pests.

If you are bothered by ants, SBB are a liability. With solids, bees will propolize every crack, and ants cannot enter. They cannot do this with SBB and ants have free access to the hive.

My design can be seen in this photo:


Cutlist and more photos in this pdf -- https://drive.google.com/file/d/0B3...MzU1LTk1YWItODIyOTMwM2I5ZDA5/edit?usp=sharing
 

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>1-Can I use a smaller screen than the #8 stuff that is standard? I have a ton of it in my cellar and I'd like to not have to buy if I don't have to. I was just thinking that the mites might not fall through.

Number 8 also works good for moths and beetles. If you find them in the bottom and smash with the hive tool.

My SBB are always closed I have a removable piece of ply wood with an aluminum tray. You can tell allot about a hive by what's in the SBB. Like if there are moths/beetles and what side of the hive. If syrup or honey is leaking. Which side of the hive the bees are working. And compare how productive they are.

Bees don't like too much ventilation new swarm or package often abscond if they have an open SBB. IMO it lets pests into the hive. There are studies that show mites breed better in low humidity hives.
 
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