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Author Topic: Are you increasing varroa population with your screened bottom board?  (Read 16084 times)
Robo
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« on: July 24, 2008, 09:40:35 AM »

I know many here believe that the screened bottom board (SBB) helps reduced varroa population because the mites fall through the SBB and can not climb back up or grab onto a passing bee.  This does seem logical, and most people without a scientific degree can visualize this process and easily buy into it. But there are studies that show the benefit of the SBB can be outweighed by the temperature drop if the SBB is left open for ventilation, both in the brood nest where the mites breed,  and in the rate of falling off bees.  So if you're using open SBB, inserting empty frames in the brood nest, using top entrance, or any other method that reduces the hive temperature, are you are helping the population of varroa grow?

I have attached two PDF files showing results of the studies if you want to read them in their entirety.

Quote from: Tucson AHB/Mites Conference RIFA Control
Temperature seems to have more of an impact on Varroa reproduction than most people thought. While 95F is "brood nest temperature," that temperature
fluctuates some with climatic conditions. By carefully controlling temperature, Varroa were found to reproduce best at 93F. Performance was a bit worse at 88-91 and 95. At the lower than brood nest temperatures, the post-capping period is extended about one day per 2F. At higher temperatures the post-capping period is not shortened significantly. However, at "brood nest" and higher temperatures, mite reproduction drops way off. In the same study it was shown that 53% of the mites on brood held at 59-68% RH (normal) reproduced normally but at humilities of 79-85% only 2% of the mites reproduced. Hot, humid brood nests are tough on Varroa. Studies of Apis cerana brood nests showed drone brood is reared at 92F (perfect for Varroa) and worker brood is incubated at 96-98F (too hot for Varroa). Purposely cooling the brood nest in Apis mellifera colonies by using a "thin" hive lid, open bottom board, simulative feeding to spread brood out, and splitting the brood nest with frames of foundation doubled the numbers of mites on the bees.



Quote from: 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

The antivarroa bottom board must never be used with its bottom hole opened as this leads to a lowering of cluster temperature resulting in ideal conditions for varroa development. As confirmed in 2000, this situation not only negated the beneficial effects of the bottom board, it also resulted in a net increase in the mite infestation rate (29.2% more varroa mites, non significant) as compared to the control group.



« Last Edit: October 13, 2009, 09:36:43 AM by Robo » Logged

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« Reply #1 on: July 24, 2008, 11:44:47 AM »

I'll get back to you  Smiley
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« Reply #2 on: July 24, 2008, 12:13:29 PM »

Thanks - good to think about, keep an open mind to different techniques. In the end, I'm for the ones that work.
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« Reply #3 on: July 24, 2008, 02:07:16 PM »

Rob, OK, wow.  I mentioned in another post I switched all my screened bottomboards back to solid bottomboards.  Now I am further glad that I did that.  My reasons for switching back were for ease of vapourizing oxalic acid though.  I don't doubt for a minute that research that you put into your post.  Cluster heat is extremely important. 

I had very low mite counts this spring, probably because I have reverted back to the solid bottomboards and vapourizing last fall.  I had performed one treatment of vapourizing, when there was no brood present, so as to get all the mites.  Vapourizing can be performed when brood is present, it does not kill brood, as the oxalic acid trickling will.  My preference was to vapourize when brood rearing had ceased. 

My curious side though.  Why did you make another post, quoting your original post?  Nosey old me.  Have the most beautiful day, loving and living this great life.  Cindi
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« Reply #4 on: July 24, 2008, 02:43:29 PM »

Robo,
Thanks for posting this.  I think you've saved the lives of a couple of queens.
We have Russians, do not use medication, and up to this point are not having problems with mites.  Some are Russians from a breeder queen, and some are the result of the Russians we purchased in the past and open breeding between established hives and ferals.  Was a big believer in SBB's and had been using them faithfully up until the middle of last year as the number of hives grew and I didn't keep up with converting the used solid bottoms over to SBB's when setting up a new hive.  We now have 48 hives including full hives and a few splits.  Less than half of our hives now have SBB's and have not noticed any difference in mite problems between the two.  I have noticed a couple of mites in our 2 TBH hives and yes, they have screened bottoms.  Not enough of a problem to worry about, just a mite or 2 here and there, more than I've noticed in our regular hives.  Might possibly be mistaken, but I would assume a TBH with open bottoms would be cooler than a 2 deep hive with supers.  Both queens are new this year, daughters of the original TBH colony queen we overwintered and not quite as dark in color as most of our Russians.  I was ready to kill these queens and blame it on bad genetics, but this report gives us cause to wonder if they might do better in a standard hive.  Was planning on using a couple of our breeder offspring to replace them.  Might continue with that plan now, but not kill the other queens, move them into another hive just to see what happens, and see how the breeder offspring do in the TBH's.  Or I could just close up the TBH bottoms. Undecided
Have a well established real strong feral hive we cut out of an old building this spring that was healthy and is still in the same condition on solid bottoms.  I realized none of this is proof of anything, but sure gives one reason to wonder.
Thanks again for posting this.
Arvin
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« Reply #5 on: July 24, 2008, 08:13:33 PM »

In my experience, I see no difference in mite levels with or without the SBB.  There is research to support both views (more or less mites).  But I think any difference is at best, negligible.  However with the SBB I can get them to stop bearding without having to buy slatted racks and I can use a tray under it to monitor and if you're using ANY Varroa treatment you will get rid of more.  Research I've seen presented by Dr. Tom Webster has shown that the Apistan resistant mites are knocked down by the Apistan, but with a solid bottom board, they climb back up into the hive again.  With a SBB they do not.  The same is probably true of any kind of treatment.
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« Reply #6 on: July 25, 2008, 02:38:50 PM »

Anecdotaly, my hives have experienced huge mite explosion the past 3 weeks. It has been the hottest, most humid July I can recall. Many, many days above 95F w/ heat indices above 100F. Some of my hives have SBB, some not, some slatted racks and some w/ vented tops-some have all 3. All of my hives are infested right now. If brood temps were as greatly impacted as written, my hives w/ traditional equipment should have less mites given the extreme weather we have been experiencing. I might just do a count this weekend and see.
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« Reply #7 on: July 26, 2008, 03:02:06 AM »

Wouldn't keeping the mite board in all the time give, in the now all too immortal words of Miley Cyrus: the best of both worlds?
« Last Edit: July 26, 2008, 04:28:59 AM by SgtMaj » Logged
Robo
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« Reply #8 on: July 26, 2008, 08:19:29 AM »

Yes, if you keep on top of it and clean it out.  As we have discussed in other threads rolleyes,  it makes a great environment for wax moths with pollen and other debris collecting there and is protected from the bees.   You can also find ants and other bugs accessing it too.   It is not practical for large operations,  but if you have a few hives and can take the time to clean them every week or so it does have it's benefits.
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« Reply #9 on: July 26, 2008, 09:40:27 AM »

Yup, although coating it with a mix of veggie oil and that wax moth chemical Annette got... you might be able to get away with not cleaning it out quite as often... though, since it's so easy to clean, one might as well do so at every inspection anyway (especially since it's also a great way to monitor problems like varroa, shb, and moths... I would think anyone would be curious enough to at least pull it out and look with every visit to the hive).

Speaking of those moths though, has anyone lined their SBB mite boards with parchment paper?  If so, do you ever find any of the wax moths boring through it?  Or does the thin bit of silicone coating on the parchment paper stop them from boring?
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« Reply #10 on: July 26, 2008, 08:11:42 PM »

[quote author=Robo link=topic=16851.msg123059#msg123059 date=121690683   
I know many here believe that the screened bottom board (SBB) helps reduced varroa population because the mites fall through the SBB and can not climb back up or grab onto a passing bee.  This does seem logical, and most people without a scientific degree can visualize this process and easily buy into it. But there are studies that show the benefit of the SBB can be outweighed by the temperature drop if the SBB is left open for ventilation, both in the brood nest where the mites breed,  and in the rate of falling off bees.  So if your using open SBB, inserting empty frames in the brood nest, using top entrance, or any other method that reduces the hive temperature, are you are helping the population of varroa grow?

I have attached two PDF files showing results of the studies if you want to read them in their entirety.

Quote from: Tucson AHB/Mites Conference RIFA Control
Temperature seems to have more of an impact on Varroa reproduction than most people thought. While 95F is "brood nest temperature," that temperature
fluctuates some with climatic conditions. By carefully controlling temperature, Varroa were found to reproduce best at 93F. Performance was a bit worse at 88-91 and 95. At the lower than brood nest temperatures, the post-capping period is extended about one day per 2F. At higher temperatures the post-capping period is not shortened significantly. However, at "brood nest" and higher temperatures, mite reproduction drops way off. In the same study it was shown that 53% of the mites on brood held at 59-68% RH (normal) reproduced normally but at humilities of 79-85% only 2% of the mites reproduced. Hot, humid brood nests are tough on Varroa. Studies of Apis cerana brood nests showed drone brood is reared at 92F (perfect for Varroa) and worker brood is incubated at 96-98F (too hot for Varroa). Purposely cooling the brood nest in Apis mellifera colonies by using a "thin" hive lid, open bottom board, simulative feeding to spread brood out, and splitting the brood nest with frames of foundation doubled the numbers of mites on the bees.



Quote from: 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

The antivarroa bottom board must never be used with its bottom hole opened as this leads to a lowering of cluster temperature resulting in ideal conditions for varroa development. As confirmed in 2000, this situation not only negated the beneficial effects of the bottom board, it also resulted in a net increase in the mite infestation rate (29.2% more varroa mites, non significant) as compared to the control group.

Great news but THINK . are you going to put heaters under the hives at night to keep varoa mites down Huh Bees dont like 95 thats why they keep brood temp down , and bees bussy fanning are not cleaning the hive . I will use the SBB in my area becouse it works for me .Everything that smells roses isn't . Smiley



[/quote]
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Robo
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« Reply #11 on: July 27, 2008, 08:26:39 AM »

Great news but THINK .
That's exactly why I posted this.  We have many new beekeepers here and I wanted to give them more information so that they can make an informed decision for themselves and not just from anecdotal advice.

Quote
are you going to put heaters under the hives at night to keep varoa mites down Huh
Bees maintain the brood temperature regardless of the time of day.

Quote
Bees dont like 95 thats why they keep brood temp down , and bees bussy fanning are not cleaning the hive .
From the research I've read, 35C (95F) seems to be the optimal brood rearing temperature.

Do you have any issues with the humidity aspect of these findings?

Quote
I will use the SBB in my area becouse it works for me .Everything that smells roses isn't . Smiley
Glad it works for you. I'm not looking to convert anyone either way,  just sharing information for those who like as much information as possible before making their own decision.
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« Reply #12 on: July 28, 2008, 12:57:41 PM »

Sharing information is a wonderful thing.  It allows the human being to made INFORMED decisions.  I don't see anything about trying to convert anyone to anything here.  It is information sharing, beautiful!!!  Have that great and wonderful day, Cindi
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There are strange things done in the midnight sun by the men who moil for gold.  The Arctic trails have their secret tales that would make your blood run cold.  The Northern Lights have seen queer sights, but the queerest they ever did see, what the night on the marge of Lake Lebarge, I cremated Sam McGee.  Robert Service
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« Reply #13 on: July 29, 2008, 01:21:32 AM »

Even though it does take extra effort, I will continue to use SBB. 

In my locations moisture is a serious concern (well actually it isn't because my hives have such good ventilation with the SBB). I don't like dampness in my hives, it leaves too much opportunity to harbor disease and pests. I have not had dampness issues like caulk/stone brood as other local beekeepers have experienced and a significant difference is that I run all SBB, he does not.

Improving hygienic genetics in one's bee stocks helps greatly in minimizing varroa in the first place.
A small level of mites maintains a good genetic 'pressure' to keep mite fighting genes. My heavy mite loads are concentrated in feral swarm colonies or cut-outs, and yet I don't see heavy mite loading as a result of drift.

I see a significant amount of chewed cappings, loose pollen, and other debris that falls through.
These are all things that my bees did not have to waste time in house keeping to be rid of.
That means the bees were doing something more meaningful - like waving to me as I arrive to inspect their hive.  Keep in mind my SBB are custom and span the entire 16x20 area of the box.

Besides, SBB make it easy to smoke a hive before/during inspection.

I think a calculated break in the brood cycle does significantly more to minimize mites then a SBB contributes, but I believe they help.

I am not sold on anyone's temperature theories. I think the thermodynamics of hive are far more complex than most scientists model. I also feel it is far more complex and conditional to other hive conditions (curing honey, pupating brood, fermenting pollen, etc.) than most models could accurately depict (it varies frm hive to hive).

If my bees were suffering from too much ventilation, they would propolize the entrances to compensate.
I have to figure that brood temps are acceptable and correct.

Keep in mind that 50% of all satistics can be manipulated 90% of the time to slant towards the results that creates the most controvesy and press (right or wrong).
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« Reply #14 on: July 29, 2008, 11:56:20 AM »

NWIN. Thanks could not said anny better  Wink
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« Reply #15 on: July 30, 2008, 11:01:48 AM »


In my locations moisture is a serious concern (well actually it isn't because my hives have such good ventilation with the SBB). I don't like dampness in my hives, it leaves too much opportunity to harbor disease and pests. I have not had dampness issues like caulk/stone brood as other local beekeepers have experienced and a significant difference is that I run all SBB, he does not.
Sounds like the anecdotal advice I referred to previously.  How about other climate differences like elevation, wind, sun exposure, etc.  or even basic differences in management styles.  Could any of these have a larger affect than you assume?   I have yards just miles apart that have enough differences in weather to affect their productivity.

Quote
Improving hygienic genetics in one's bee stocks helps greatly in minimizing varroa in the first place.
A small level of mites maintains a good genetic 'pressure' to keep mite fighting genes. My heavy mite loads are concentrated in feral swarm colonies or cut-outs, and yet I don't see heavy mite loading as a result of drift.
Sure, hygienic behavior plays a part in it as well. My experience has also been that some feral colonies can have fairly high mite levels.

Quote
I see a significant amount of chewed cappings, loose pollen, and other debris that falls through.
These are all things that my bees did not have to waste time in house keeping to be rid of.
That means the bees were doing something more meaningful - like waving to me as I arrive to inspect their hive.  Keep in mind my SBB are custom and span the entire 16x20 area of the box.

Or possibly spending their time and resources keeping the brood temperature up?

Quote
Besides, SBB make it easy to smoke a hive before/during inspection.

true

Quote
I think a calculated break in the brood cycle does significantly more to minimize mites then a SBB contributes, but I believe they help.

Absolutely,  I personally think that plays a large roll in how the ferals are surviving.  Every swarm they throw is a break in the brood cycle.

Quote
I am not sold on anyone's temperature theories. I think the thermodynamics of hive are far more complex than most scientists model. I also feel it is far more complex and conditional to other hive conditions (curing honey, pupating brood, fermenting pollen, etc.) than most models could accurately depict (it varies frm hive to hive).
I don't necessarily disagree that it is more complex than what we know.  But I do consider it higher than "I use SBB and he doesn't, so that is why" when deciding on my approach.

Quote
If my bees were suffering from too much ventilation, they would propolize the entrances to compensate.
I have to figure that brood temps are acceptable and correct.

Or they are burning additional resources maintaining the core brood temperature.  B Heinrich determined that even free swarms regulate their core temperature to 35C.  It may even be that a large portion of the honey they gorge on before swarming is used for this thermoregulation.

Quote
Keep in mind that 50% of all satistics can be manipulated 90% of the time to slant towards the results that creates the most controvesy and press (right or wrong).
Agree, that is why each needs to make their own decision.  Hopefully based on data from multiple sources and not just anecdotal advice.
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« Reply #16 on: July 31, 2008, 02:53:57 AM »

Or they are burning additional resources maintaining the core brood temperature.  B Heinrich determined that even free swarms regulate their core temperature to 35C.  It may even be that a large portion of the honey they gorge on before swarming is used for this thermoregulation.

Unless your average daytime temps were above 35C, in which case it would seem logical that it might help them keep from consuming more resources to provide A/C for the brood.  Of course, day and night temps. vary greatly, so even then if one was going for maximum efficiency, I guess they would need to be constantly inserting and removing the mite board... which would be very tedious.  On the other hand, armed with that knowledge, a thermostat, and a clock, an observant person could figure out how long the temperature remains above 35C at different daytime highs in your area.  Then you can figure out at what point the temp stays at or above 35C for exactly 1/2 of the day.  Then for example, if you see the temps being forcasted are at or above that level all week, you could leave the mite board out to gain efficiency.  The rest of the time you could leave it in.  And this probably only applies to tropical and subtropical climates only, as I would think that most US climates stay below 35C most of the time.
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« Reply #17 on: July 31, 2008, 10:50:12 AM »

Well I have both types of bottom boards, some are screened and some are solid Pressure treated plywood on clipped pallets. The hives with the highest mite counts in May were the ones with SBB. The SBB hives also took longer to draw the frames out to the bottom bar but did not need to have the bottoms cleaned like I always have to do on the solid ones. I prefer the clipped pallets over a single hive configuration any day. just a 2 cent observation.
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« Reply #18 on: July 31, 2008, 11:11:52 AM »

Dallas, Don't laugh but what is a "clipped pallet?"  embarassed (well, you can snigger a bit if you want..) rolleyes  Jody
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« Reply #19 on: July 31, 2008, 12:04:23 PM »

The pallets that I built basically will allow me to place 4 hives on it and pick them up at one time with a loader. They are similar to a fork lift pallet you see behind stores except that they are smaller and have a solid bottom for use as a bottom board for the colony. The clips are used to keep the box from shifting on the pallet keeping it all together. I also have seen some made with screen in the bottom board. I will try to get a couple of pics for ya.
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