# For those of you who use Oxalic Acid..



## enjambres (Jun 30, 2013)

I think of varroa control as a year-round thing.

I start my year with a single vaporization in late December or early January. This is a bit later than many people but I like to make sure my bees are done flying around picking up fresh mites from feral colonies they are robbing from.

OAV at this point in your colony's life cycle is terrifically effective killing nearly all of the varroa in the colony since none are protected by being under the cappingd with since there is no capped brood.

This (most of the time) keeps my colonies (mostly) clear of mites until mid to late summer.

At that point the mites start to build up. if they build up fast I'll use something else (MAQS) that is more effective at killing mites under cappings and can be used with honey supers on. If the build-up is slower - or I am feeling like taking a risk I wait until late August or early Sept. and start a four dose series on 5 or 6 day intervals.

But bear in mind I monitor my mite populations on every colony, every single week of the year, so I can afford to take a more watch and wait approach than would be safe if I only tested irregularly.

Some falls we never seem to get to winter and the bees keep flying out of the apiary, so sometimes I'll throw in another 3-dose series in late Oct or early N ov to keep things under control.

I really like my Varrox. Since you have one, you know it's a sturdy permanent tool, and it sounds like you got a bargain.

Be sure to buy the required personal safety equipment: a respirator with ACID GAS cartridges, and don't fail to wear it each and every time. In other posts I have described my OAV techniques in extreme detail. Search for them and you'll know all my secrets.

Enj.


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## BPadelski (Jan 13, 2017)

enjambres said:


> I think of varroa control as a year-round thing.
> 
> I start my year with a single vaporization in late December or early January. This is a bit later than many people but I like to make sure my bees are done flying around picking up fresh mites from feral colonies they are robbing from.
> 
> ...



Thanks man, I appreciate it. Helpful stuff there. One buddy of mine treats his hives 3 times a year with OA in a series of 3 treatments every 7 days. So his first treatment will be day one and the last one day 21. I'm assuming this is so he treats all stages of the brood all the way until the bee emerges. He will treat April, July and October before winter. Where can I buy a respirator like that with the cartridges?!


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## enjambres (Jun 30, 2013)

Actually if he treats three times, on seven day intervals, his last treatment is on the fifteenth day from the first treatment. So just barely enough to catch the emerging mites that happened to be capped with drone brood on the day of the first vaporization.

It's a common error to think of it as 21 days (what's three times seven???), but there only two seven-day intervals between the first and last treatment, with one other treatment day smack in the middle, if you do a series of three treatments. (I usually ask my students to look at their hand and tell me how many spaces are between their five fingers - they always answer four, of course. Same thing with three treatments: one less interval than the number of treatments.) 

You can buy a half-face respirator at some or big box big box stores like Lowes or HD. Mine is my 3M and I believe it take 6293 cartridges. You can also buy the mask on Amazon. The key here is ACID GAS cartridges, sometimes they stand alone and sometimes they are paired with organic vapor capabilities. That's OK, as long as they are clearly marked for ACID GAS (even though you're doing something we call vaporization is actually a sublimation.) Trust me, you need ACID GAS. The cartridges need to be replaced from time to time, depending on your usage of the mask. I get at least a year out of mine, and I treat about 40 colonies between mine, my students' and those of my beekeeping friends. 

Take the time to get the mask adjusted to fit right, and check the fit every time you put it on, even if you've just taken it off a few minutes before. I used to be a volunteer firefighter who did interior attack, so checking my breathing gear over and over is second nature but I have to keep drilling it into my students' heads.

Enj.


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## BPadelski (Jan 13, 2017)

Thank you for the reply. Good info.And yes you are right. It would the the 1st, 8th and 15th day. Thank you for the correction.


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## Tenbears (May 15, 2012)

I do pretty much the same as Enj, except I stress doing my mid winter treatment on a day when it warms up to flying temperatures. Those Indian summers or mid winter thaw we always seem to have in January are perfect times.

Here is my reasoning: I want to get the job done in a single treatment. It reduces stress on the bees. A tightly clustered colony of bees does not allow the OAV gasses to reach the entire colony. Although the bees can be treated at any temperature above 37F The cluster is pretty tight until the ambient temperature rises above 50. by treating on those days the loosened or broken cluster allows for better saturation of AOV thus a more effective single treatment. 

I do my fall or mid summer dearth (depending on mite loads) treatments with OAV also. MAQS works well But I had a problem with it and queens a few years ago, So I decided to go other route. 
I do three treatments at 8 days. The first treatment gets 90% of the Phoretic Mites (mites living on bees or related spaces) On the 8th day the treatment gets 90% of the mites that have emerged from capped brood over that period along with mites that may not have been got during the first treatment. The last treatment 16 days get the mites what have emerged within the final 8 days. Since emerged mites remain Phoretic for two weeks their will be very few in capped cells at this time. Because drone brood remains capped for 13 to 15 days It is a fairly certain bet that very few mites would be in capped cells. My tolerance thresholds are considerable lower that most recommendations. and I rarely exceed them by more than 10% when early fall treatment arrives. Leading me to believe this procedure offers good hive protection. IMHO


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## Munson (Mar 16, 2014)

Side note: One of the "correct" masks from amazon is:
Safety Works 817663 Multi-Purpose Respirator (Ideal for working with ... certain acid gases)
and yearly refills
MSA 815364 Advantage Chemical and Combination Cartridge, Organic Vapor, Acid Gas, P100 Filter Type (Pack of 2)


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## nediver (May 26, 2013)

Really great advice on this thread. 

I do exactly what has been discussed. I don't monitor mites though. I treat winter when broodless. Late fall when broodless. And summer, but sometimes MAQS instead. Varrox. Respirator with organic cartridges.


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## aunt betty (May 4, 2015)

The farm stores sell the masks for acid vapors. Farm and Fleet has them on sale 15% off right now.
Rural King. Tractor Supply, and Big R probably sell them as well.
I'd been setting the battery upwind of the hives, connecting the leads, then run into the house or truck (upwind) with my timer running. It takes 30 seconds to a minute for the vapors to start. Using a smoker to figure out which way the wind is blowing before treating is part of the program. Now I have a really nice 3M mask. Cost around $35.


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## enjambres (Jun 30, 2013)

Seeking shelter - as opposed to wearing the correct mask - may work OK, except if a problem develops during the burn. Then what you going to do? Expose yourself or risk some type of damage to the bees?

Masks cost $35 - bees and their hives cost far more, and your health is priceless. 

Get the mask with the right canisters. And not those rated just for organic vapor, BTW, you need ACID GAS canisters. Don't confuse the wording here. It is not vapor (despite what we call the process), and the "organic" descriptor is talking about the classification of the material's origins in chemistry, not it's state at the time of the burn. Sometimes ACID GAS canisters are also good for organic vapors (dual-use types). That's fine, just don't use organic vapor-only canisters. Those won't do the job. Read the package inserts or call the manufacturer's #800 number.

I'm very glad Aunt Betty now has a good 3M mask. I nag and nag about this because I want to harass every OAV user on BS into using the right safety equipment. 

Nagging is what old dames like me do when we've lost the power of sex appeal. Deal with it!

Enj.


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## baybee (Jan 10, 2016)

If enough OA vapor shows outside the hive for a mask to be required then probably an extra towel is necessary to tuck around the wand and all the ventilation openings should be closed too. Remember that OA is a strong acid: it can not only burn one's lungs but also the eyes. Does your mask cover the eyes too? If not, you aren't 100% safe.


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## igottagetalife (Feb 19, 2012)

So besides OA either (D or V) what other treatments, if any do you use in your apiary? I have friends in Belgium and France who keep bees and only used OA and they are now finding mites that are resistant to it...is that possible?


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## nediver (May 26, 2013)

I have the Magenta/Yellow 3M P100 Filter says "certain" organic vapors/acid gas. 

I hope that works?


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## Dlight (Mar 12, 2017)

I have seen people use foggers to treat for mites is there any way you could use a mixture of OA to use in a fogger to treat for varoa


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## baybee (Jan 10, 2016)

> So besides OA either (D or V) what other treatments, if any do you use in your apiary? I have friends in Belgium and France who keep bees and only used OA and they are now finding mites that are resistant to it...is that possible?


http://www.beesource.com/forums/showthread.php?331279-OAV-Resistance

May have nothing to do with resistance of mites to acid, rather with the race/breed of bees.


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## iluvicecream (Jun 2, 2014)

I do one OAV treatment in December and three in March spaced out a week. After the supers are removed, I place a Mite Away Quick Strip (MAQS) between the two brood boxes. I know that you can do MAQS with the supers on...but that's a lot of boxes to take off for me!


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## Norcalkyle (Apr 23, 2015)

4X in late July and 4x in late October.


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## markus2 (Nov 6, 2015)

enjambres said:


> I think of varroa control as a year-round thing.
> 
> I start my year with a single vaporization in late December or early January. This is a bit later than many people but I like to make sure my bees are done flying around picking up fresh mites from feral colonies they are robbing from.
> 
> ...


Although I also did my last OAV treatment in December...I am curious about the OAV treatment during the December /January time frame. If the bees are in a tight cluster, do you feel that the vapors can effectively penetrate the cluster?


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## snl (Nov 20, 2009)

markus2 said:


> Although I also did my last OAV treatment in December...I am curious about the OAV treatment during the December /January time frame. If the bees are in a tight cluster, do you feel that the vapors can effectively penetrate the cluster?


Yes, but remember, you can only do OAV when the temps are 37 and above. The cluster is not so "tight" that the vapors will not penetrate.


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## msl (Sep 6, 2016)

SNL out of curiosity, were does that number come from?
at 37, I would suppose the cluster in a reduced entrance polystyrene foam hive would be different from a wood one with a open SBB..
like wise out here a dark painted hive in full sun would be different then one in full shade


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## snl (Nov 20, 2009)

msl said:


> SNL out of curiosity, were does that number come from?
> at 37,


That comes from BioVet (the make of the Varrox and other beekeeping items). But it is also widely reported by other scientific studies. But we're talking outside temps...


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## Cheryl (Mar 18, 2017)

Have any of you had plastic frames melt from the heat generated in the hive from the Varrox? I use wooden slatted racks and screened bottom boards and could also vaporize from top.


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## msl (Sep 6, 2016)

snl said:


> But we're talking outside temps...


right, thats what I am getting at.... the internal temp is going to varrie widely by hive set up and climate.. I see the 37 tossed around a lot. do you have a link to some of those scientific studies?


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## snl (Nov 20, 2009)

msl said:


> right, thats what I am getting at.... the internal temp is going to varrie widely by hive set up and climate.. I see the 37 tossed around a lot. do you have a link to some of those scientific studies?


I don't know about vary "widely," as the cluster heat for the hives remains relatively stable. The bees don't really heat the inside of the hive, they maintain a cluster temp. 

http://www.apidologie.org/articles/apido/pdf/2006/01/M6010.pdf


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## costigaj (Oct 28, 2015)

Dlight said:


> I have seen people use foggers to treat for mites is there any way you could use a mixture of OA to use in a fogger to treat for varoa


Probably, but you may die using it. Getting in your skin is not comfortable and getting it in your lungs is not good.


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## msl (Sep 6, 2016)

snl said:


> I don't know about vary "widely,"


Even if the air temp is same, a hive with a open SBB on foggy New England morning is going to be different then a hive with solid board a reduced entrance on a sunny CO afternoon. 

(just quicly scanning) The link you posted says it was tested in range of 35.6 F to 60.8F, and gives no data on air temp vs efficiency of treatment. the only thing of instrest I see in the study is they were treating below the "given" 37 F number. 
I have off seen 40f as a "given" number as well ... my curiosity has gotten the best of me and I am looking for a study to back up the 'given" numbers


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## aunt betty (May 4, 2015)

igottagetalife said:


> So besides OA either (D or V) what other treatments, if any do you use in your apiary? I have friends in Belgium and France who keep bees and only used OA and they are now finding mites that are resistant to it...is that possible?


I suppose if the mites are wearing rubber boots to keep their feet from being burned off then they'd be resistant. 
In other words...I don't think so.

The resistance is most likely poorly done treatments in hives with very large brood chambers. There is an Iowa guy in Beesource who has experienced poor results from OAV because he runs huge colonies with three deeps of brood. More capped pupating larva means more mites survive.


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## snl (Nov 20, 2009)

msl said:


> I have off seen 40f as a "given" number as well ... my curiosity has gotten the best of me and I am looking for a study to back up the 'given" numbers


https://www.sussex.ac.uk/webteam/ga...atmentoxalicacid-a4-1page-2016(2).pdf&site=60


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## msl (Sep 6, 2016)

Thanks....
However, They are saying 39.2F is the lower limit, further more they state that above 60f its too hot to ply OAV. When you look up their study they claim to be basing the temp recommendation on the 1st link you posted. 

The 1st link says the limit is 37.4 for OAD and 35.6 for OAV, but doesn't provide any data to back that up

so for what ever reason the 2nd link is pulling the 39.2f out of their butt or miss qoating the 1st study...either way there claim of 39.2 is baseless as there sited sorece doesn't back it up. 


so back to square one, there is a rule of thumb, but I can't find anything to back it up, and neither link supports the 37F number


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## markus2 (Nov 6, 2015)

snl said:


> I don't know about vary "widely," as the cluster heat for the hives remains relatively stable. The bees don't really heat the inside of the hive, they maintain a cluster temp.
> 
> http://www.apidologie.org/articles/apido/pdf/2006/01/M6010.pdf


Although the bees are heating the internal cluster temperature... the escaped heat from the cluster certainly helps with the ambient temperature of the internals of the hive. I have experimented with 2 different sized hive clusters. The hive hardware was identical but the cluster size wasn't. I've used temperature sensors and hive heaters to prove this theory out. I was quite surprised at how much heat is given off from a higher population of bees.


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## igottagetalife (Feb 19, 2012)

Bees only heat the cluster not the hive.... 37 outside is 37 inside, if bright and sunny and dark paint maybe slightly warmer but I would think it would be marginal. 

Right? or what am I missing?


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## JTGaraas (Jun 7, 2014)

Whenever I see temperatures given in decimals such as "37.4 for OAD and 35.6 for OAV", I assume two (2) things: (1) there was a conversion from Celsius to Fahrenheit and the writer thinks .4 or .6 degrees is important (but it is insignificant and such an amount will not make me put on or take off a jacket), and (2) putting water on bees makes more sense when it's warmer. Not being a scientist, but having 69 experiences with North Dakota winters, has taught me to avoid getting anything wet when it is cold - OAV will always make more sense to me when anywhere close to freezing, and also, the hive is more likely broodless.


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## shinbone (Jul 5, 2011)

igottagetalife said:


> I have friends in Belgium and France who keep bees and only used OA and they are now finding mites that are resistant to it...is that possible?


There are no credible reports of resistance to OA. If a person is having trouble killing mites with OA, it is because he/she is not applying it properly. It does take some practice to apply the stuff in an effective manner.


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## shinbone (Jul 5, 2011)

enjambres said:


> Nagging is what old dames like me do when we've lost the power of sex appeal. Deal with it!
> 
> Enj.


I am sure you still have plenty of sex appeal. 




.


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## shinbone (Jul 5, 2011)

msl said:


> right, thats what I am getting at.... the internal temp is going to varrie widely by hive set up and climate.. I see the 37 tossed around a lot. do you have a link to some of those scientific studies?


msl - I understand your desire for clarity and precision, and for scientific support of conclusions - when you say internal temperature will vary widely, how much variation is there and how was it determined?

I ask because the bee cluster is not a static object subject only to the whims of atmospheric conditions. Rather, the bees actively work to maintain a certain temperature range within the cluster and/or on the brood comb. There is then heat leakage from the heating bees which provides heat within the hive box, etc. In other words, while it is safe to say there will be temperature variation within the hive box, it is also true that there is a lot of thermal activity specifically designed to offset such temperature variation. The end result being it is not clear to me how much temperature variation there actually is.



.


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## John Davis (Apr 29, 2014)

The cluster effect starts as the temp goes down. The bees gather together to keep themselves warm. The cluster gets tighter as the temp decreases. In the 40 degree range the cluster itself is still "loose" enough for the vapors to penetrate and treat the internal bees. There are less heater bees head down in the cells. It's not a critical temp number that causes harm.


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## msl (Sep 6, 2016)

John Davis said:


> The cluster gets tighter as the temp decreases. In the 40 degree range the cluster itself is still "loose" enough for the vapors to penetrate and treat the internal bees.


I under stand what is "said" but I have yet to see a single study to back that up.

SNL stated 37 as


> widely reported by other scientific studies.


 but no one has yet to provide a link to such a study
the 2nd link he provided said *you should't OAV above 60f!!!* but I don't see that getting passed around as common knowledge yet the same link is being used as support for 37-40f 

shin- lay a sheet a plywood up on the roof with an air gap, feel the back side on a sunny afternoon and then on a cloudy one.. solar gain matters...
now does it make a difference... who knows I don't know that 40 is any better or worse then 30 or 50 
point was bees do give off heat, the more closed up and insluated the hive the warmer the internal temp, the loouser the cluster 

I may have side tracked my self...but the direction I was going was a hive with a SBB may need a higher air temp then one that is sold, and a hive in full sun may get away with a lower temp

I should end this with saying I am NOT trying to take a shot at SNL, he just made a handy platform for me to challenge established "facts"


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## snl (Nov 20, 2009)

Another report of temperature to use OA.. Not sure of a "study" per se.... but reports of temps by reputable sources

http://www.dave-cushman.net/bee/oxalicthorne.html


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## snl (Nov 20, 2009)

From Randy Oliver.....why to vaporize above freezing temps.

At near-freezing temperatures, the passive units may not get the vapors to penetrate the cluster, so active units were developed. Some use 12-volt current and a fan, and some propane, to force the fumes into the cluster. Again, some fog does blow out of the hive, so the beekeeper must exercise extra caution not to be exposed to it. One critical aspect of both types of vaporizers is that the colonies must be tightly sealed in order to keep the vapor inside, since vapor that escapes obviously does not work to kill mites.


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## msl (Sep 6, 2016)

Randy's qoate would leave one to think the ProVap 110 may be useabull at lower temps then passive units


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## snl (Nov 20, 2009)

msl said:


> Randy's qoate would leave one to think the ProVap 110 may be useabull at lower temps then passive units


Possibly, but why would you want to vap at those lower temps.... unless you had no choice.


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## shinbone (Jul 5, 2011)

msl said:


> shin- lay a sheet a plywood up on the roof with an air gap, feel the back side on a sunny afternoon and then on a cloudy one.. solar gain matters...
> now does it make a difference... who knows I don't know that 40 is any better or worse then 30 or 50
> point was bees do give off heat, the more closed up and insluated the hive the warmer the internal temp, the loouser the cluster


Are you sure solar gain matters? What studies can you point to, to support that statement? This small study shows that the solar gain affect is negligible, despite all the yammering people tend to do about it, and is of any benefit only in the extreme climates where every little bit may help.:

http://www.beesource.com/forums/showthread.php?293979-Solar-Gain-Tests&highlight=solar+gain

The point I was trying to gently make is that you are holding people to a higher standard than you are holding yourself. By that I mean you ask a question based on unsupported assumptions, and then you want people to point to scientific studies to answer you. Double standard. 

Obviously, people can ask any question based on anything they want, but true scientific studies in bee science are expensive to do, and thus few and far between. I am not trying to tell you or anyone else how to manage their bees. But beekeepers tend to be pragmatic and use what they have found works or what other people have found works. Requiring a full scientific study before taking action means the "rigorous" beekeeper will be housing bees in hollow logs for a long time.

JMHO


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## markus2 (Nov 6, 2015)

igottagetalife said:


> Bees only heat the cluster not the hive.... 37 outside is 37 inside, if bright and sunny and dark paint maybe slightly warmer but I would think it would be marginal.
> 
> Right? or what am I missing?


There are a few factors that I can think of when comparing outside ambient temps to inside hive temperatures. 
1. The number of bees in that hive. 
2. How well insulated that hive is. 
3. The current outside temperature. 
4. How big the openings are to the hive. 
5. How windy it is outside of the hive.

Basically, the better insulated that hive is...the bigger the temperature differential between the ambient temps of inside vs outside. There may be other factors that I'm not thinking of.


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## msl (Sep 6, 2016)

shinbone said:


> The point I was trying to gently make is that you are holding people to a higher standard than you are holding yourself. By that I mean you ask a question based on unsupported assumptions, and then you want people to point to scientific studies to answer you. Double standard.


not my intent in the least..witch was the point of my comet


msl said:


> now does it make a difference... who knows


 In light of your constructive criticism I would change "vary widely" to "vary" as I have no proo of just how wide the difrence is
However there is plenty of support for solar gain and insulation effecting the cluster, so I don't under stand how you can say its an unsupported assumption


> From closer study of the data taken during periods of relatively constant temperature it was concluded that solar radiation markedly affected cluster movement





> 7 A colony protected by insulation will have a less compact cluster that will fluctuate more in size with temperature change than a cluster in an unprotected colony


The Thermology of Wintering Honey Bee Colonies, Charles D. Owens, U.S. Agricultural Research Service, 1971

your study is great!
And to the point there was a 10 degree difference on a cloudy day, did you get a number for a sunny day? 

Its obvious I have run off on a tangent from my intentinch:


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