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Derek Mitchell article discussing effect of higher humidity on varroa

18K views 121 replies 15 participants last post by  Litsinger 
#1 ·
Derek Mitchell has another research article that addresses hive configuration and its impacts on humidity. Apparently, it also covers the implications of higher humidity on varroa reproduction.

https://royalsocietypublishing.org/doi/10.1098/rsif.2019.0048

From the abstract:

"It is highly likely that honeybees, in temperate climates and in their natural home, with much smaller thermal conductance and entrance, can achieve higher humidities more easily and more frequently than in man-made hives. As a consequence, it is possible that Varroa destructor, a parasite implicated in the spread of pathogenic viruses and colony collapse, which loses fecundity at absolute humidities of 4.3 kPa (approx. 30 gm−3) and above, is impacted by the more frequent occurrence of higher humidities in these low conductance, small entrance nests."
 
#2 ·
Possibility of CO2 and/or humidity being a factor is often mentioned.
For sure, bees in the trees have much better control of both as well as higher presence of both (vs. the commercial hives, since we are so crazy about "ventilation").
One reason I really want to trial a Warre-formatted hive, but built similar to this:
https://www.youtube.com/watch?v=tV90sHPOd70
 
#3 ·
One reason I really want to trial a Warre-formatted hive, but built similar to this:
https://www.youtube.com/watch?v=tV90sHPOd70
Interesting video, GregV. Initially I thought we were looking at thin-walled hive bodies but then I realized that the top super had a rabbet along the whole perimeter of the box to receive the plastic? inner sheeting. Also it may be based on the width of the top bars, but it looks like his frame spacing is wider? Maybe 1-1/2" center-to-center?
 
#4 ·
Unsure of his center to center.
Pretty sure standard 35mm (1-3/8).
The top bars, however, are metal pipe about 1/2 inch - this allows for pass-thru up and down.
These thin top bar create an illusion of wider frame (the are not really).

He has two hive formats:
* 12 frame (the original format)
* 8 frame (this one the author favors now as he is an older dude).

The box walls are compatible to our 2x wood.

The clear heavy plastic completely seals the top.
Lately he switched to using clear silicon film, actually - a great idea.
I think this material is like silicon rubber and thinking get some and test it.
Check it out - great specs, about ideal:
https://www.amazon.com/Silicone-Rub...ocphy=9018945&hvtargid=pla-441001201172&psc=1
 
#6 ·
8-frame square;
silicon completely seals the top;
metal plate - helps to condense the water by cooling off the seal - this is early summer and condensation is very good help for brood rearing;
notice how bees do NOT propolise the film between the combs - NOT needed - the non-permeable seal is already in place
https://www.youtube.com/watch?v=WLduRE96S_U

PS: the propolise pushing researchers should watch this video and think - WHY is it bees not propolising the film over the brood nest???
because it is NOT needed and they will not spend the time/effort doing it if the surface is already satisfactory in sealing the nest
Yes - very unhealthy - no propolise ..... - I am being sarcastic now.

For this exact reason they will propolise my burlap completely - to seal it closed.
 
#11 ·
There is an article in the Feb.-ABJ by Bill Hesbach on ventilation of the Condensing Colony that ties in nicely with these articles about high humidity and varroa control. It definetly has changed my view of top and bottom ventilation- especially for Winter. Makes you think about the old rules of top and bottom ventilation.
I'd like to hear others views.
Jerry
 
#12 ·
I'd like to hear others views.
Jerry:

Good post- I saw their is an accessible online article from Mr. Hesbach here:

https://www.beeculture.com/winter-management/

For my part I have a mix of standard Langstroth hives that I run with a top entrance consisting of a single 1" diameter hole and Warre hives with a single 7/8" diameter hole in each and every box.

I have found that in preparation for Winter all colonies will work to partially occlude the openings but rarely close them off completely.

Further they seem to be constantly working on the openings, adding and removing the propolis plug as overwintering progresses.

Based on this completely anecdotal feedback I've concluded that they know what they want and I let them open or close the openings as they see fit.

It also does appear that they tend to utilize the upper entrance preferentially for cleansing flights in the Winter, so there might be some marginal benefit there.

What do you observe in your locale?
 
#13 ·
I'm in the process of converting my timetable to be OTS freindly. I'm also reconfiguring my hives to be closer to natural beehives. More insulation summer and winter and entrances on the sides , half way up. no upper or lower entrances. I really think the bees will thank me.
Way to much cold wet dripping on bees the way we've been ventilating. Going to change some things
Jerry
 
#19 ·
Way to much cold wet dripping on bees the way we've been ventilating. Going to change some things
Good thread, Jerry. It is interesting and helpful to read about how others are approaching this issue. I imagine that the 'right' answer may at least in part have something to do with one's specific climate and weather patterns.

For my part (as previously noted) I run top and bottom entrances on all hives and the bees respond by laying down propolis in varying degrees to the upper entrance in preparation for colder weather (example photos attached) and seem to be continually monkeying with the opening size (with no discernible pattern) throughout the winter.

This winter (and based on the success of others on this forum), I decided to add 1" closed-cell foam insulation to the colonies for added benefit, with some worry that this might lead to the accumulation of condensation above the cluster.

On one of our recent mild days, I popped the tops and to my joy only found two colonies with condensation on the inner cover- in both cases it was in the corners and not over the cluster, which squares with what I believe CLong has observed with his highly-insulated assemblies.

I do sincerely hope you are able to find a hive set-up that provides reliable condensation control in your locale, and I look forward to reading about your experiments.

Russ

Pest Wood
Insect Pest Stain
Wood Birdhouse
Wood Stain Carpenter bee
Eye Iris
 
#14 ·
I have not had a duel vent hive in three years; choosing to have a bottom vent only. I have been trying for several years to define the design requirements for an enclosure for honey bees. "Homeostasis", year round, sums all the issues in a neat definition. Defining the variables is not easy but I think I am approaching a new level - seeing homeostasis within a hive - but still have a lot to learn. I need more sensors in more hives. Existing data out there helps a lot, leap-frogging doubts, when I know how to ask a question of Google Scholar; Seeley, Mitchell, Ellis,Tautz, Mobus all have a lot to offer. Hesbach offers some good explanations.

My trend is simply emulation of typical tree hive characteristics but larger volumes, different materials. Do not underestimate the effect of wind on heat transfer, both convective heat transfer coefficients and tidal / mass flow effects. I am becoming a believer in conservation of water within a hive and buffering characteristics. I don't like plastic only nor more vents, propolis is amazing. Observation: It is amazing how fast moisture leaves a hive when it is cold and dry outside - my bees forage for water anytime it is above 40F and sunny, sometimes grey skies (dehydration issues?). I live in a wet area near the ocean and have a lot more to learn, so it seems. Best of luck to all who experiment ( and everyone else) this coming Spring.
 
#15 ·
Robert-
Sounds like your asking a lot of the same questions a lot of us are pondering. I've got almost all 8 frame equipment and I'm really glad I went that way because of the way I'm thinking of wintering my bees starting next year. Taller , narrower, better insulated, a3-4 inch deep area between the bottom board and brood area and only one entrance - 1x3 inches-- half the way up the hive into the brood area. Radical? Not according to mother nature.Top- heavy insulation with a short spacer for natural air circulation and patty feeding. Natural warm air of the hive will circulate across the top and down the sides for condensation on the sides instead of dripping from top.
Just my ideas for next winter. Sick of losing bees (7 this winter). Going to do a lot of things different the next 6 months
Jerry
 
#16 ·
Jerry: I cannot comment on 8 frame versus 10 except form a concept point of view. Horizontally there is less insulation but that is easily accounted for by sizing insulation. I put a 2 inch spacer on top of my propolized 12 oz. duck cloth - inner cover . I put my remote sensor here on the canvass. I also loosely pack in some old cotton tee-shirts. ( Shades of a quilt box approach but no direct venting) I soon realized I have created some sort of" tree like" topping. I have watched water collect on the top canvass, eliminated that issue and then the I have watched the RH change slowly with ambient weather. RH is always high in this top zone but temperatures just below the dew point - a controlled water vapor buffer zone? It is also very curious that the colonies have raised the canvas on short, top bar columns of waxy propolis providing circulation like passage ways, I think.

I feed heavily in the Fall to "weight" ( see M. Palmer). I am going to modify by canvass inner cover by adding a central hole to allow emergency or early Spring syrup feeding if necessary. It will also be useful for installing sensors and probing quickly. I currently stick a simple dial thermometer ($5.00) in each hive top canvass as a simple data point and verification the colony is alive.
 
#18 ·
I have been feeding water back to my hives since December either through a wet sponge on the landing board or from spritzing their sugar bricks. So while they now have a dry cavity I’m reevaluating the top entrance again if I already have vent holes and vivaldi quilt box.

Just read the ABJ article. Wondering again how much colony death has more to do with dehydration then starvation aided by hive design. The well known “they were surrounded by honey but couldn’t move” problem. Maybe they couldn’t metabolize their food from lack of water and humidity.
 
#23 ·
One thing I have learned, invariably it is always more than one issue. One head sometimes rises higher. Maybe they wee not albel to move to warm food. The primary tools of a honey bee are heat generation, fanning and sensors. If honey temperature ( an dinternal ambient) is down, say 25F for exaggeration purposes, how are they going to consume it, get to it? Once bees can establish temperature control in a volume they tailor it to their needs. This assumes no real mechanical issue like an iced covered entrance/exit for days. Once temperature control is established they work hard on humidity control. IMO, those who cannot establish humidity control by foraging for water, raising brood for more water or control moisture losses die of dehydration. I strongly favor a one hole design; bottom is my choice. I "think" ( no data) mid or top is OK but a little more stressful in winter as the cluster needs to adjust.

Pick up, bare handed, an apparent dead bee outside the hive in cold weather. One that looks perfectly normal but cannot move (I do this to check for diseases occasionally). Sometimes they will start to twitch - a leg, antennae movement. Cusp it for a minute or more and open - you will see more motion. Do it long enough with a little sun and they can fly away. Some go right back to the snow and die ( altruistic suicide due to disease?) . Some head for the entrance or a sunny spot or I place them on an entrance so they can decide. It all starts with head temperature followed by thorax, then abdomen.
 
#24 ·
Jerry, My entrance is a bottom mounted vertical, sliding plate with about 7-8 holes big enough for a drone to exit (7/32 -1/4"). This is in conjunction with a bottom screen board with a sticky board (3/8" gap between screen and sticky board in place all winter, most of summer. My side insulation is now 2-inch XPS and the top is now 4-inches think. No top venting but temp and humidity sensors on 3 hives, temp sensor on most hives. I intend, this year, to test full side insulation on ~1/2 of my 9 hives this year with the other half having top insulation only - starting about June 1 after last frost. Hope it helps - it has been a warm, wet winter this year and raining/fog as I type. (A few years ago 6 Ft. accumulation, typically 2 feet but been changing - wide range).
 
#25 ·
Clong - "All insulation stays on all year long." Can you offer any observations, positive and negative experiences?

My casual observation of a poly-nuc is it is a poor moisture buffer and collects water. I also see extra vent holes, front and rear for this type of design (had closed rear but soon opened it). But heat / temeprature control increases brood rearing significantly. I am building wood nucs with glued on XPS foam insulation.
 
#26 ·
Robert,

I didn't notice anything negative. I never noticed any moisture on the inner cover. I flipped it to the notched side in late May or early June, thinking it would help the bees to remove moisture. This year I plan to keep it shut.

My bees are in 80% shade during spring/summer. I didn't see any mold, or obvious signs of distress in the poly hive. They made 75 lbs of honey, which is my best performer to date.

My question is how do the bees get 100s of pounds of moisture out of the hive? I've never seen any water trickling out. Do the bees carry it out?
 
#27 ·
I do have a handle on net pounds of water by method but the primary mode, I think, is the difference in vapor pressure between inside the hive and outside. Basically when the inside is warmer (hot and moist or higher RH) than outside ( cold and dry or low RH), then the hived drives water vapor out via the entrance / vent holes like a water faucet ( likely mixing mechanically and by diffusion, inside with cold dry air first. Moisture vapor also penetrates the wood box walls (permeation) and is stored or lost. You do not see water vapor until it condenses as in a cloud which is water droplets. Fanning, especially in summer time removes moisture from honey or when cooling the hive by causing a flow of moist air out. Pictures tell the story better - Dept of Energy has stuff on house moisture which is the same technique. In winter, I think condensation in the cold zone, below the cluster, also contributes as well as cleansing flights (bees store water in their poop). Wind pressure variations cause what I call "tidal flow" causes air to flow in and out of the entrance ( you fell it on a windy day opening the door you house. Top vents with a bottom entrance have a chimney effect that constantly pulls moisture and heat out of the hive, 24 hours a day - people have reported seeing it condensing at the top vent.

The more I read, the more is seems that dehydration is the big problem - crazy eh? I have been able to see the effect of moisture loss in a reduction in RH when days are cold with low RH. It is a process that continues for days not minutes and hours. A researcher a the turn of the century saw the effect with simple mercury thermometers and weighting scales. He was trying to measure honey consumption but his data was distorted by hive weight changes due to moisture absorption. Weight would go up sometimes and then drop significantly over a number of days - in winter. Wood is good buffer or storage material for water as it takes and gives back slowly through the propolis layer if the wind does not rob it all. Of course the modes vary with the season; summer, honey, flying bees and lots of brood is a lot different than winter clusters and little brood.

Hope this helps.
 
#29 ·
Mostly airborne from what I can figure out. I cannot give you a number-yet. Bees on cleansing flights are dropping water with the poop but as they fly the loose moisture to the air. It would seem a small amount gets to the ground from condensation and popping.

To eliminate water from a hive, the hive has to be warmer and more moist then the outside. When it is hot, raining or foggy, and close to or at 100@% relative humidity outside during a hot summer day the moisture flow reverses. Uncapped honey will absorb water, wood will absorb water, brood cells will absorb water(brood cocoons), stored it in poop chamber. Fortunately rain usually cools the air below 95F giving the bees some margin to manage with - lots of fanning. I have measured the top of my supers at 99 - 102F, brood chamber is 93-95F rock solid and you can hear the hummmmmmmmmmh. When liquid water evaporates it takes a lot of heat to do it.
 
#30 ·
Robert- For those of us that are going to insulate-2" on top and sides - and run solid bottom boards - one bottom entrance-- would insulation under the bottom board affect the natural moist air flow down the insides of the hive? Or would leaving the bottom board exposed underneath to the outside temp be ok?
Jerry
 
#31 ·
I have not looked at that, insulated bottom nor tested that approach. I am testing no insulation on the bottom becasue I like a cold bottom concept as a water condenser. But, I do no think it, solid bottom , no insulation, is that far different than my current approach of small entrance holes and a screened bottom board with sticky board in place -essentially a cold bottom, no bottom insulation. I can tell you that the air temperature drops as you go down a hive - significantly, even with insulation on the sides. Warm moist air rises and of course clusters in winter are like wood stoves with a pot of water on top. I have an air-gap between the hive boxes and the insulation. A good sized cluster with brood ( I think) will keep the air-gap at 60 F on top and 50 F at the bottom, smaller clusters seem to hold it in the 50F region with mor evariations. How good is the wood stove ? that's the unknown.

I use to do some testing in an environmental chamber the size of a long shipping container. The moisture generator was about a 3 inch glass tube with a heater and dripping water inside. Being steel, the container did not lose much water vapor. We could control the relative humdity and temperature (40F to 120F) and make it rain. I do not remember a blower ( fanning) on the glass tube, I think is was just diffusion by vapor pressure differentials - like a whistling tea pot or a boiling pot of water. It seemingly only needs a small hole to casue flow - logical!?
 
#32 ·
Good ideas - I'm pretty sure I know what my insulated cavity is going to look like now. I thank you for your input. I'll let you know how the construction is going. Remodeling older equipment mostly Got part of it done. Will have 12deeps- tops and bottoms and insulated to move some of my bees into this Spring thanks again
Jerry
 
#34 · (Edited)
Bumping this up for a review. Lots of good info links spread thru the thread. Some questions answered about insulation staying on year around; No it wont cook your bees! Has anyone seen reports of bad results from people who have tried more insulation and less ventilation? I have not seen much barring my own experience with having hives totally iced in with frozen slush which is a highly unusual situation. Gray Goose may have got hit with the same weather and same bad results.
 
#35 ·
Hi everyone - it's been a long busy Spring- Summer and Fall. Every time I'd convince myself to sit down and post my current activities something else would demand my attention. This retirement thing can get awfully hectic.;)
I did get most of my hives reconfigured into med. - deep - med. - as I wanted last Spring. One round opening in the top of the bottom med. - no top opening and 2" of foam insulation on top. Ended up with 19 put together this way. I lost 12 hives through the winter, last winter, using my old configuration with a small vent hole on the top and bottom.
I then split 10 of the strongest hives in mid-May and sold those Nucs in June. Almost all of the other hives I split into 2-3 and 4 hives and Nucs around the 1st of June. Sold 5 of those Nucs in July. This was all done by producing my own queen cells by several different Queen pulling methods. ( Mel Dissoelkoen). The hives that I split in May all produced 80 - 100 lbs of honey. A few of the other June splits produced an x-tra box too.
All hives - all summer were in med.- deep - med. and supers above that. One small opening in pollen box and 2" foam on top. (Walt Wright) Last Spring I didn't do any checkerboarding (Nectar Management) - I was to busy reconfiguring the hives. Next year- I'm going to try to leave some of my July Nucs for 5 over 5 Nucs and overwinter them that way. All my Nuc boxes are sitting empty in the garage- kind of a waste. I will also be CBing in April.
Treated everything with OA in August after harvest. No high mite counts ( I credit the brood breaks all of my hives had). Will be doing mite counts in Spring and plan on treating high counts. (OA) I also believe that the high temps and high humidity in the hives has helped keep the mite counts low. I don't have the equipment to know that for sure but the majority of my hives looked strong going into winter. All had brood in the central deep and strong stores in the top med. I did feed heavy in Oct.
So that's been my year along with U-pick strawberries- raspberries and deer hunting. (shot an elk in Wyoming in Sept.:D ). Expansion year for me. We'll see what Spring brings.
Have a happy and prosperous New Year!
Jerry
 
#36 ·
Hi everyone - it's been a long busy Spring- Summer and Fall. Every time I'd convince myself to sit down and post my current activities something else would demand my attention. This retirement thing can get awfully hectic.;)
I did get most of my hives reconfigured into med. - deep - med. - as I wanted last Spring. One round opening in the top of the bottom med. - no top opening and 2" of foam insulation on top. Ended up with 19 put together this way. I lost 12 hives through the winter, last winter, using my old configuration with a small vent hole on the top and bottom.
I then split 10 of the strongest hives in mid-May and sold those Nucs in June. Almost all of the other hives I split into 2-3 and 4 hives and Nucs around the 1st of June. Sold 5 of those Nucs in July. This was all done by producing my own queen cells by several different Queen pulling methods. ( Mel Dissoelkoen). The hives that I split in May all produced 80 - 100 lbs of honey. A few of the other June splits produced an x-tra box too.
All hives - all summer were in med.- deep - med. and supers above that. One small opening in pollen box and 2" foam on top. (Walt Wright) Last Spring I didn't do any checkerboarding (Nectar Management) - I was to busy reconfiguring the hives. Next year- I'm going to try to leave some of my July Nucs for 5 over 5 Nucs and overwinter them that way. All my Nuc boxes are sitting empty in the garage- kind of a waste. I will also be CBing in April.
Treated everything with OA in August after harvest. No high mite counts ( I credit the brood breaks all of my hives had). Will be doing mite counts in Spring and plan on treating high counts. (OA) I also believe that the high temps and high humidity in the hives has helped keep the mite counts low. I don't have the equipment to know that for sure but the majority of my hives looked strong going into winter. All had brood in the central deep and strong stores in the top med. I did feed heavy in Oct.
So that's been my year along with U-pick strawberries- raspberries and deer hunting. (shot an elk in Wyoming in Sept.:D ). Expansion year for me. We'll see what Spring brings.
Have a happy and prosperous New Year!
Jerry
Great feedback Jerry,
I am jelly of the Elk harvest that is still on my bucket list.

hope the spring ends up with lots of strong hives.

GG
 
#39 ·
I have seen the article by Mr. Hesbach on different forums. Many people successfully take a different approach to ventilation but I have not seen his theories trashed to any extent. There is a vast difference in local conditions experienced by members here, from no winter to 6 months with very few opportunities to fly. For some, winter is not much of an issue.

The more honey the bees have to consume to achieve desired cluster temperature and humidity concerns, the more gut waste they have to hold onto or else soil the frames.

Cost and simplicity of winter preparations is very important if you have more than a handful of hives. Perfection can be the enemy of practicality.
 
#40 ·
Perfection can be the enemy of practicality.
Agreed.
This is where I am likely to stumble. I want the perfect hive. I don't have so much umph to experiment at this time, so I keep beating the bushes here on Beesource for guidance- and it's been great so far.

For example, I heard on Beesource that bees didn't predictably use the OTS notch to draw queen cells so, I put it to the test this season and found that to be true. I had used OTS for several years just assuming it worked great.

This looking for perfection is leading to some culling of what doesn't work very well.

The local weather is very significant to me. February in Kansas, before any real bloom happens, it can get warm enough for flight one week and the next it might be -20F for two weeks then back up again.
 
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