Thermal Control of Varroa and SHB - Blog version - Pictures and graphs removed

Updated: Mar 4, 2020

For the full article with pictures and supporting graphs, visit (removed for blog post) Presents:

Thermal Treatment Review

Mites, Small Hive Beetles, and MORE??? :-)

Beekeeping Stories: An adventure in Integrated Pest Management

An article and review by Mike Immer for

Please be sure to get permission from and credit the author and source when


Special thanks to Sophia A. Immer for some assistance making graphical sense out of

my junky spreadsheets! (removed for blog post)

Article Summary/Overview:

Thermal treatment equipment and methods vary. The thermal boards from are simple and require little to no custom or

non-standard equipment.

Thermal treatment on 30 test colonies showed the greatest effectiveness on both

varroa mites and small hive beetles (SHB) on single brood box configurations.

Thermal treatment was still effective for varroa mites on double deep brood boxes

configurations but was less effective for small hive beetles (SHB).

Thermal treatment was more difficult and less effective for varroa mites and made

almost no difference for small hive beetles (SHB) in triple deep configurations.

Additional, more anecdotal information offered: general health and hardiness of

bees observed to be better and support the proposed additional benefits of reducing

the viral and bacterial load bees may be experiencing with mites being the primary

vector for the additional diseases. Testing to continue on this topic.

Pros: Kills mites on the bees, in the hive, even under capped brood

Kills or forces out small hive beetles (SHB)

Less safety equipment is required/more comfortable

Safer than oxalic acid sublimation/dribble

More studied and proven than essential oils and powdered sugar methods

Less temperature dependent than some treatment methods

Can be used with supers

Durable and reusable

Can be integrated with other pest management methods if needed

Length of treatment ensures impact on mites as foragers come and go*

Affects mites on bearded bees with temperatures that kill or sterilize mites

Recent studies indicate that heat can also reduce viral and/or bacterial loads

No need to buy and store harsh chemicals or worry about expiring products

~$350 US per unit

Cons: Length of treatment (roughly 2.5-3 hours) and yes, listed as both pro and con

Requires monitoring for 15-30 minutes until treatment temp is reached

Requires power (nearby outlet or generator)

Only available for Langstroth style 8 Frame, 10 Frame and Nucs

Custom bottom board required to treat plastic/foam insulated hives

Recommended operating temperature minimum 70 degrees Fahrenheit

(Meaning most treatments done in daytime when foragers are out)*

Effectiveness varies based on configuration of hives l

(Meaning most effective on singles, least effective on triples)

Doubles and triples often require tape over any gaps between boxes

~$350 US per unit - and yes, this is listed as both pro and con

*Note: Reiterating the biggest complaint about the process and product, the

treatment time. This may actually be a positive in regards to overall effectiveness.

Most foragers will be making trips back into the hive to deposit any gathered

resources over this period of time and will be exposed to the raised hive

temperature. The temperature to sterilize mites is actually lower than the full

treatment temperature, and less exposure time can still effectively reduce or

eliminate mites in a given hive/colony.

Returning foragers may also beard up with the other bees trying to regulate the hive

temperature, and thus be exposed to temperatures that can kill or sterilize mites

they already had, or those they may have picked up while robbing out a collapsed

hive, open feeding, or just being out foraging in the trees, flowers, etc.

Records/Data: See my somewhat rudimentary spreadsheet data and cost

comparison at the end. One or two hives being tested wouldn’t be a large enough

sample, so I used 30, in the same yard. Further, more scientific studies could

eliminate more variables by standardizing further and providing a control. (removed for blog post)

Disclaimer: I am not a scientist or a professional researcher, data analyst, or even a

spreadsheet guru. I’m an “ok” writer I suppose, but I know there are errors here and

there in this article correcting would have put publication of this information off

EVEN LONGER. The curse of a perfectionist with very little time I guess!

That said, I know there are unaccounted for variables, and likely anomalous data

due to my own terrible handwriting, the weather, etc. J But certain trends and

generalities can be gained from the data I’m offering as it relates to the small scale

testing that I did on thirty of my own colonies in the summer and fall of 2018.

Thumbnails (below) are of the larger graphs at the end of the document: (removed for blog post)

The Rest of the Story - for those that like to read

First of all, I am not what you would call a strictly, treatment free beekeeper.

By strictest definition, treatment free beekeeping advocates discourage ANY type of

activity that intervenes in the process of bees developing their own survival traits

against pests like varroa and small hive beetles. Some would argue that anything

beyond observing them in the wild could be considered intervention. So I won’t get

into that.

Although I applaud treatment free or chemical free beekeeper’s determination and

intent in some ways, and I LOVE the idea of treatment free beekeeping…I like the

idea of keeping bees alive even better!

Even so, I try to keep a “no judgment” attitude in my little bee company as I try to

help whoever I can, without condemning “mite bombs” and the increased potential

for small hive beetle proliferation, and spreading of other diseases etc.

I just try to be as responsible a beekeeper as I can be, and take care of my bees, and

my customer’s bees, as well as I can.

That said, and even though I use things like Apivar, oxalic acid sublimation/dribble,

patties, test other methods etc., I DO like to limit the use of harsh chemicals when I


In fact, I tend to favor more natural and organic treatments whenever I can… IF they

are effective.

So, in thinking about this mysterious new thing called “thermal treatment” what

could be more natural and chemical free than strait up heat? Right?

I’ll go ahead and risk sounding (unintentionally) like a review of the specific type of

thermal treatment equipment I tested, but this article is more than that.

Hopefully I will be able to relieve some of the immediate concerns beekeepers seem to have beyond the general “newfangled-ness” (if that’s a word) of these computer

controlled devices.

A lot of beekeepers have never heard of thermal treatment.

In fact, I’ve received lots of private messages about this topic, so thought I’d go

ahead and write up my experience and elaborate a bit for whoever is interested.

When I first came across thermal treatment, I had NO IDEA what it was, how it

worked, it’s intended use etc. other than it was a relatively new and chemical free

alternative treatment for honeybees to rid them of the nasty little varroa mites that

have been causing such difficulty and disease.

It turns out that the bees themselves do a version of “thermal treatment” when they

swarm, raising the hive and their own body temperatures before they go, etc.

Fascinating, right? Did you know that? I didn’t until I started my research!

I did a ton of reading, and it turns out that the concept isn’t necessarily new, but

overcoming some of the challenges during the studies and finding a way of

simplifying the process IS new.

To boil down a LOT of research, some of which was conducted in other countries,

thermal treatment simply involved heating bees up to determine at which

temperatures mites were affected, and at what temperatures would the bees, brood,

wax, queen, etc. be able tolerate?

You can imagine how many bees “gave their lives” in this type of research. It’s kind

of sad to think about.

You can imagine, there were significant difficulties encountered in rounding up

bees, moving them, containing them for treatment, building cabinets for treatment

and monitoring, and then putting survivors back, and determining queen viability,

managing variables, laboratory versus field studies, etc.

Moreover, there was lot of measuring and recording of data to determine what

temperatures and timeframes were required to kill mites in various states and

various places within the hive. For instance, finding ways of killing mites under the

capped brood, where they are protected from many other treatments!

By the way, this is the real breeding ground for varroa mites, that many other

treatment methods don’t reach. This one very good reason that oxalic acid (OA)

vaporization (more accurately called sublimation) and fogging aren’t very effective,

at least when brood is present! That is also why several treatments are necessary.

The every four days, or every seven days, for three or four treatments with OA? That

is intended to get into the cells that were capped, and hatched, etc. over the

treatment period! That may be something else you didn’t know too!

So, before we get into too much detail, I think the simple goal of all of this, beyond

healthier bees, should be stated:

Use heat to destroy/control mites, and have healthy and productive bees.

Without going into the “law of unintended consequences” and a bunch of other stuff,

let me outline some of the reasons I landed on one particular product to test with.

1. I didn’t want to utilize ANY non-standard beekeeping hive equipment. If it

required custom frames or foundations, I had no interest in trying it.

2. I wanted use ONLY standard Langstroth deeps, mediums and even a few

shallows, in ten and eight frame configurations as these are the most

common, and would provide the best test for my own purposes based on

what equipment and bees I had available.

3. Portability is important as I also didn’t want to have some kind of bulky

enclosure or cabinet to move around, or a process that could only be used at

night, or anything like that.

Why? Like most beekeepers, budget always plays a role. All of my equipment at the

time consisted of standard, Langstroth deeps, mediums, and shallows, with a mix of

plastic frames, plastic foundations, wooden frames, and even some foundationless

frames. And I also had very few telescoping lids by this time, as I had switched to

migratory lids.

After doing some looking, I chose the “Mighty

Mite” thermal treatment boards.

I spent a lot of time at their website reading through their documentation before

deciding to go this direction. The information they shared matched up pretty nicely

to other studies I’d read, and even used some of those studies as sources.

Since I had both eight and ten frame equipment, I went ahead and ordered one of

each. This would allow me to treat two hives at a time, which it turns out was hugely

beneficial to me as I had already determined I wanted to test thirty hives.

This particular piece of equipment met my needs for simplicity, no custom

beekeeping woodenware, etc. and it was simple to install.

But there were (and are) some requirements to consider.

1. You need a power source, either a standard outlet nearby, long enough to run

extension cords, or a generator.

2. You need to make sure the ambient temperature is 70 degrees or higher.

3. You may need some tape for any gaps, and an extra super to set on top of the

provided foam lid to hold it down while providing adequate ventilation.

4. Notably absent from these requirements? Chemical resistant gloves, eye

protection suitable for fog/vapor/sublimation, and a respirator.

Since I was running mostly singles, I started with a couple of those and decided to

test it’s effectiveness on the doubles and triples I had, last. Since customers had been

asking, and I was investing the time and money into testing these devices, I was

determined to keep records as well as I could.

(Assuming my chicken scratch, glove and wind hampered notes can be trusted, I’ll

provide what I was able to translate into spreadsheet data at the end!)

It’s important to note that the following experience as a first time user of thermal

treatment, although common, isn’t necessarily representative of a typical treatment.

I’m just relating what I did, how I did it to some extent, and why.

But it makes for an entertaining story that can save time for users of this product

who, having read this, will know better what happens, and what parts of the process

will continue on WITHOUT the intense scrutiny I’m describing.

And yes, I did a mite wash and counted nine on the first hive prior to treatment.

As you can imagine, I was very cautious with my first treatments to be very sure I was doing this correctly. And I remember, my goal was to test this process, so starting with a “before” alcohol mite wash was an important step.

I reviewed the instructions and got to work.

I slid the thermal board/heating plate into the fully open entrance easily. It fit nicely and sat solidly on the bottom board, covering the screen on the first hive. (I had a mix of both screened and solid bottom boards.)

Following the directions closely, I placed the sensor on

top of the middle frame of the bottom brood box, which was easy enough given that

I was starting with singles. Then I made sure the connection to the control unit was good.

I put the provided insulation board on top instead of the migratory lid, and then placed an empty medium on top of the foam insulation board to hold it in place, and placed the migratory lid back on top of the empty super, leaving it gapped, or open by a couple of inches to make sure it was well vented. And since my first test was on a single, I didn’t have to worry about taping/sealing any gaps between brood boxes etc.

I put the specially provided entrance reducer on the front. It was designed so that it

had just enough room for the cable to the heating element on one side and only

enough room for a bee or two at a time to make their way in and out of the opening

at the other side.

This special reducer was intended to keep the heat in and make it harder for

the bees to work against the process while the hive was getting up to

treatment temperature.

Nervously, I plugged in the control unit last, and three lights blinked as the

computerized controller did a “Power On Self Test”. I was one button push away

from starting the process. So, I gave it one last look and started it up.

What was going to happen??? Would all of my wax melt? Would my bees pile up dead? Would my queen abscond, stop laying, or worse let, lose viability or die???? Scary stuff, right? :-)

I watched, intently while the blinking blue light indicated it wasn’t yet up to the correct temperature.

A few bees started piling up a little at the much smaller entrance as it took fifteen to twenty minutes to switch from blinking blue to blinking green

indicating the hive had reached treatment temperature.

I pulled the entrance reducer out a couple inches and stood back to watch…and

watch…and watch…

The green light blinked red a few times indicating that the temperature in the brood

nest had reached a tenth of a degree higher than the target, and the thermal board had turned off and stopped heating for a while. As the temperature came back down

to the ideal 106 degrees, the green light resumed it’s blinking.

The beard on the front of the hive got bigger, and bigger as more and more bees piled out in a futile attempt to lower the hive temperature.

And more and more foragers were coming in to deposit the resources they had gathered.

It made sense on seeing this why ventilation is SO important. Imagine how much oxygen the bees use to try and cool down their hive into the normal range! If the hive was sealed too tightly, asphyxiation would be a risk!

This cycle continued…and continued…and continued…for two and a half hours!

That’s a LOT of time, right?

But not to worry! I was only sticking around for the full cycle because it was my

first time using it.

As I gained more confidence and experience I was able to start the process, and once

the entrance reducer was pulled away, I could walk away, go do other things (like

start a second hive’s thermal treatment process, and just let the treatment complete

on it’s own.

Please note that it is CRITICAL to make sure the ventilation is correct, and to

remove the entrance reducer once the hive reaches treatment temperature. So set

an alarm on your phone or something! (That’s what I did).

While observing the process, and watching the bees beard more and more, I also

noticed something else that was fascinating…

Small hive beetles were LEAVING the hive, right out the front entrance, and

right into direct sunlight!

But more about SHB later.