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Freezing wax moth eggs: how long does it take?

This morning a reader pointed out inconsistencies in my website. In one post I wrote, “Freeze honey combs before storing. The USDA recommends 24 hours at 0 degrees F.”

In another post I write, “To kill the moth [eggs], you must monitor both time and temperature. For example, the Mid-Atlantic Apiculture Research and Extension Consortium (MAAREC) publishes the following guidelines to kill both species of wax moth: “20 degrees F for 4.5 hours or 5 degrees F for 2 hours.”

The reader wanted to know, “So which is it?”

The real answer

The real answer here is “neither” or “both,” depending on how you look at it. These numbers—like so many others in beekeeping—are recommendations or guidelines. They are not rules carved in stone. You’ve certainly heard advertisements that end with the phrase “results may vary,” right? Well, that applies to nearly any beekeeping recommendation, including these.

Most of the time, science doesn’t reveal simplicity. Instead, it exposes complexity. In a simple situation like freezing wax moth eggs, there are far too many variables to give a cookbook answer.

I had a statistics professor in graduate school who loved the word “exogenous.” He would stand in front of the class and hold on to the second syllable as long as he could: ex-ahhhhhhh-gen-ous. His point was that nothing goes uninfluenced by other things. So when your experiment doesn’t work, you say “Ahhhhhhhh! It’s those ex-ahhhhhhh-gen-ous variables!”

So what is an exogenous variable?

Simply stated, an exogenous variable is something that originates from the outside. In this case, factors not measured or considered in an experiment are affecting the results.

The results listed above give the times and temperatures that were needed to freeze wax moth eggs in two different freezers in two different places by, I imagine, two different researchers.

That the results are slightly different is not at all surprising. Of course they are different. If they were exactly the same, I wouldn’t trust either one of them. Exogenous variables, variables not measured in the experiments, affected the results.

Name a variable that wasn’t measured

Now, I don’t know what those variables were. There are probably many, but over breakfast this morning we came up with some possibilities.

    • Thermometers: they read differently. Go to a store display of thermometers and take a look.
    • People: some may read the thermometer carefully, some may round, or there may be parallax.
    • The temperature of the freezer: is it close to your target temperature or much colder?
    • The freezing cycle: how warm and how cold does the freezer get during each cycle of operation?
    • Defrost cycle: if the defrost cycle runs when the frames are in there, freezing will take longer.
    • Temperature of the combs going in: if they are 80 degrees, freezing will take longer than if they are 60 degrees.
    • Opening and closing: if the freezer is opened frequently, freezing will take longer.
    • How deep in the freezer are the frames: deeper placement means less influence from opening and closing.
    • Packing arrangement: If frames are packed tightly, freezing will take longer.
    • Condition of the freezer gasket: if it’s old and worn, it may leak, so freezing takes longer.
    • Amount of frost in the freezer; frost is an insulator and could change the rate of freezing.
    • Front near the gasket could create an air leak and decrease the rate of freezing.
    • Size of the load: if you add many frames at once, they will take longer to freeze.
    • Thickness of the combs: thicker combs will take longer to freeze.
    • Frame wraps: if you wrap the frames heavily, they will take longer to freeze.
    • Condition of moth eggs: are they full of water or are they beginning to dehydrate?
    • Mass of freezer contents: if lots of frozen goods are in there, the new additions will freeze faster.

I’m sure you can think of others. But as you can see, it would be impossible to calculate all the influences. Instead, we write guidelines that work for most people most of the time. Are they failsafe? Of course not.

So what should I do?

People often ask how I do it. In truth, I don’t look at the time, temperature, or anything else. I wrap my frames in plastic film and then place them in the freezer overnight. The next morning, I take them out. Without removing the wrap, I let them thaw at room temperature and then store them in a cool room. Period. I’ve never had a problem.

But remember, that is my freezer. Yours will be different. If you think the freezing was sufficient to damage the wax moths eggs, you are good to go. If not, leave them in longer. Freeze them until you are happy. Freezing them longer won’t hurt anything at all.

Rusty
Honey Bee Suite

Freezing wax moths eggs prevents the growth of larvae.
Freezing wax moth eggs prevents the growth of larvae. Wax moth larvae are an unpleasant addition to your comb honey, although I hear they are good for fishing. Pixabay public domain photo.

Comments

Richard Soundy
Reply

You said: “Wax moth larvae are an unpleasant addition to your comb honey, although I hear they are good for fishing” You under-estimate the value of wax months and basically, the bees know how to handle them, because the bees know the benefits. I produce them by the millions…..

Rusty
Reply

Richard,

Hmm. I agree that honey bees can handle wax moths, but when your harvested comb honey is sitting on your kitchen table, there are no bees. Not in my house, anyway.

Barb
Reply

Wax moth larvae are just plain creepy! They also can and will chew through Ziploc bags if the comb is not frozen which I recently discovered. The wax appeared to be intact but crumbled to a fine powder when touched. Moths and larvae in all stages from wax comb removed from the hive in January. They are resilient, I’ll give them that.

ignasi orobitg gene
Reply

Thanks for the lesson.

The wax moth is a fat problem that I have.

frances I Moore
Reply

Ha Rusty, why do u wrap your frames, do u or should u wrap them? This is what I do, am I messing up, I took out all the shelves in the freezer, I stick the whole hive body in the freezer it will hold 4 deeps and I let them stay in there for several days or weeks until I will need them unless I have a bunch to freeze then it is a week. my storage room is my living room

Rusty
Reply

Frances,

The reason for wrapping is storage. The freezing kills the eggs, but if the frames are stored where wax moths can reach them, they can be reinfected immediately by the next moth that comes by. If your frames are stored where no moths can reach them, then there is no danger of reinfection.

John
Reply

Excellent post and a terrific reminder that there are a lot of variables to consider. I don’t know much about wax moths, but this Michael Palmer video suggests that perhaps the type of wax moth is also a factor to consider: https://www.youtube.com/watch?v=0TU5ZvZcJhA

Rusty
Reply

John,

Very good point. The eggs of the different species will have different characteristics and different response times to freezing.

AnnMoses
Reply

Hi Rusty,

I’ve done the same thing as a moth preventative. Once a year I take as many frames as I can fit, wrap them (or not) and stick them in my freezer. 24 to 36 hours later, I take them out and put in several more until I’ve cycled through all of them.

JoeC
Reply

Time and temperature have tremendous impacts. In the science of food preservation, it is well documented that you can pasteurize products at relatively low temperature, but it takes much longer to effectively destroy the pathogens you are worried about with a low temperature/long time regimen vs. a high temperature/short time pasteurizer regimen. It has been a long time, but I remember from food science classes in the 1970’s that there were studies done on destruction of trichinosis cysts/eggs in pork. I don’t remember the details, but it would take roughly a month to destroy the eggs in temperatures just below freezing while at below 0 F temperatures it might only take a couple of days for the same effective kill and at -20 F even less time. I would be very surprised if the wax worm eggs did not respond the same way.

Rusty
Reply

Joe,

That is an excellent example of a factor I did not include in my list. Thank you!

Jan Olsson
Reply

Hey, Rusty

Also pollen-mould can be killed be freezing. Pollen comb that is to be preserved for later, can be put in a freezer (below 0 d.) for a day or two. The pollen stays fresh thereafter.

Jan Olsson, Denmark

Rusty
Reply

Jan,

I didn’t know that. Thanks. I will try it.

Mary Gervase
Reply

Two quick questions, Rusty.

Do you keep frames wrapped after freezing?
Is it best to store empty comb in a dry but sunny location or cool storeroom?
Is Nosema apis spores also killed with this freezing?
Many thanks for your immensely informative posts, Rusty. You are teaching us a lot!

Rusty
Reply

Mary,

1. Yes. The idea is that they are protected from re-infection by wax moths as long as they remain wrapped.
2. Empty combs are best protected from wax moths by exposure to light. Wax moths do not like light. Many people stack boxes in a criss-cross fashion so all the combs get light exposure.
3. No. Nosema spores are not killed by freezing.

Caleb
Reply

If you didn’t have a large enough freezer, could you use dry ice and a very good sealing ice chest? Dry ice would have the added benefit of raising the c02 levels as well as freezing cold temps.

Rusty
Reply

Caleb,

Dry ice would certainly freeze them. Some insects, honey bees included, have a very high tolerance to CO2. I’ve heard they can tolerate levels that would kill us, but I don’t know about wax moths.

JoeC
Reply

We did studies in 80 foot tall grain silos (empty ) with CO2 as a fumigant. I don’t remember the % CO2, but our test organisms would go into a hibernation state if the CO2 got too high. Best kill based on the CO2 as the only agent was considerably less than pure. It would take about a week for an effective kill under optimum conditions.

I would expect that the cold would be the primary killer in this case, but only testing would tell for sure.

Rusty
Reply

Thanks, Joe. I wish I could remember where I was reading about CO2 and honey bees, but it’s not coming to me. What you’re saying here sounds about right.

Caleb
Reply

Well, there is a mite tester that uses C02 to knock out the honey bees in a container and do a shake test that way. I have been seriously considering it because you just dump them back into the hive when you are finished and they just wake up and go back to work. I’m glad to know it wouldn’t cause them any brain damage from oxygen deprivation. Here is a video of the process:

Terry Drewery
Reply

I’ve lost 5 hives to these little demons in the last month or so. I’m a novice when it comes to beekeeping. Only had 8 hives. I froze my frames and hives for 6 days. After reading this article I’m thinking that’s enough? But I’m not sure how cold my freezer gets, it’s one from Lowe’s hardware, like you use in the house . I’m not sure if it gets down to zero. But I think after reading this that’s all I need to do?

Thanks a lot for your information it helps. Side note. I put the infected hives out by the freezer away from any bees I knew of and when I came back two days maybe three days later to put them in the freezer I found that a swarm had set up home in one of my hives (but I didn’t understand that’s what happened ), I just thought feeding bees from other hives had come to scavenge. I tried to knock them off, and i did a lot of them but there was more there. As a matter of fact I put it inside and closed the freezer door. But then after thinking about how heavy it seemed I thought there were more bees then should of been feeding and it was kind of heavy. I didn’t want to kill that many ! So I took it out and took a closer look . So now I have a new hive that I’m going to transfer over into one of the frozen hives as soon as they thaw out.

Rusty
Reply

Terry,

Wax moths are opportunistic scavengers that take advantage of weak colonies. Strong colonies can keep them in control. I wouldn’t assume that wax moths killed your colonies, but they took advantage of colonies that were already weakened. All I’m saying is that you should evaluate why your colonies may have been weak in the first place.

Charlie Abbott
Reply

thanks

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