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The Classroom

The Classroom – November 2022

- November 1, 2022 - Jamie Ellis - (excerpt)

The Classroom - ABJ - Jamie Ellis
Wax moth control

I have been a hobbyist beekeeper for over 30 years. Way back when I first started beekeeping, I was told you could protect empty supers with drawn combs from wax moths using paradichlorobenzene (PDB) moth crystals (sold as Para-Moth). I never really needed to protect many supers until this year. PDB is not a particularly dangerous chemical, but I am wondering if it is safe to use them to protect the supers from wax moths? I was thinking that the wax might absorb some of the vapors and, hence, become harmful to the bees. Do you have any information of the safety of using this material to protect the supers?

Secondly, I have been told recently that the use of Certan (Bacillus thuringiensis — Bt) is an acceptable treatment for protecting supers from wax moths. This is not a particularly dangerous material and seems like it should be a good treatment for wax moths. Do you have any information on using this material for treating supers and do you have any opinion on which method is the best treatment?

Douglas Doremus
Louisiana, August


I have used PDB crystals against wax moths in the past. In fact, this is what I used for about the first decade of my beekeeping life. You ask about the safety of the product relative to honey bees. The key with any chemical is to follow the label. A pesticide’s label is written in a manner that maximizes the product’s efficacy against the target organism (the wax moth in this case) while minimizing impacts on non-target organisms (the honey bee). PDB crystals are one of the recommended management strategies for wax moths, so they are safe to use in stored supers, pending you follow the label regarding their use.

It will be important to air out the treated supers prior to returning them to a honey bee colony. The label should include information on how to do this. When I used PDB crystals, I tended to air out the supers a few days longer than what the label suggested, just to be sure. I would also smell the combs just to confirm that I could no longer smell the compound.

Bt can be used to control wax moths. It is marketed as B402 (Certan) in the U.S. To my knowledge, this product works quite well. Let me share a bit about how this product works. Bt (Bacillus thuringiensis as you note in your question) is a bacterium that produces protein toxins that kill moths. There are different strains of Bt, with each strain’s toxin being useful for the control of a different insect pest. Most strains are used to control moths, flies, or beetles. Combs treated per the B402 label will be toxic for wax moths to consume. This product is not toxic to honey bees.

What would I do? I likely would treat half of my stored supers with Bt and the other half with PDB, just to determine what works best in my situation. You could stick with the Bt product moving forward if it performs as well as PDB crystals do. Just FYI: My preferred method of storing combs is actually in the freezer. Then, you do not need to treat the combs with anything. However, I realize this is not an option for most folks, given it can require quite a lot of freezer space depending on the number of supers that need to be treated. 

Q  Stored honey for winter food

I was listening to the September management podcast (Two Bees in a Podcast) and you kept saying make sure they will have enough stored honey. Does it have to be capped? My girls have plenty but have had trouble capping it this year.

Rob Jones
Georgia, September


Thanks for listening to my laboratory’s podcast! My co-host (Amy Vu) and I really enjoy making the podcast. Our sole motivation for doing it is to provide beekeepers an additional way of learning about honey bees. I hope all readers of this column consider checking out the podcast. I really think everyone will enjoy it, and learn something new in the process. You can find it here:

On to your question: Honey bee colonies need an appreciable amount of stored honey to survive winter. In fact, that is the very reason honey bees store honey! They use it as fuel to generate heat and energy to move.

I want to share with the reader additional information that may help them understand your question/my forthcoming answer. First, honey bees derive their energy from sugar. They get their sugar from nectar. Roughly speaking, nectar is about 80% water and 20% sugar. This high concentration of water makes nectar very unstable, given the likelihood it will ferment. Thus, bees have to reverse the water:sugar ratio of nectar to make honey. Essentially, they need to take something that is 80% water and 20% sugar and turn it into something else that is 80% sugar and 20% water (over-generalizations here, mind you).

They do this by fanning their wings at the nest entrance to evaporate some of the moisture off the nectar. This dehydration, along with the addition of various enzymes that help convert the sugars, leads to the production of honey, a product that is far more stable in the combs than is nectar. Bees cap honey once it is “ripe,” i.e., the correct moisture content. We beekeepers tend to use the capping as an indicator of how ready honey is to extract, under the assumption that capped honey will be the right moisture content, making it less likely to be too dry (granulate) or too wet (ferment).

Your question is, does it matter from a winter feed perspective? It all depends. It takes energy from sugar for the bees to be able to produce wax. Consequently, ripe honey can remain uncapped if the nectar flow stopped before all the honey was capped, meaning there was no incoming energy (nectar) to produce the cappings necessary to cap that final bit of processed honey. It is also entirely possible that the nectar was not processed fully and that it is, in fact, too “wet” to cap. If this is the case, the honey risks fermenting in the combs during winter. Bees should not eat fermented honey.

Ultimately, it is impossible for me to tell you that it will not be a problem. However, my gut tells me that your bees will likely consume this as an energy source first, and then move on to the capped honey later during winter.

Q  Different honey from different bees?

 Do different bee species make different-tasting honey or is it really related to the type of flower used to create the honey? I know bees excrete enzymes to mix with nectar to create honey. Different bee species should have different enzymes in their bodies; therefore, whatever they produce should be different.

Brandon Vu


I want to make sure I understand your question fully, so I am going to answer it a few different ways.

You ask about bee species. I assume you mean the various species of Apis? Apis is the genus for honey bees, and there are ten species of honey bees. One occurs naturally in Europe, the Middle East, and Africa. The other nine occur in Asia. The one that occurs naturally in Europe, the Middle East and Africa is Apis mellifera. This is the honey bee we have in North America. This species has also been taken to many parts of Asia. Thus, it co-occurs with the other nine species.

Where these species co-occur, their honey can be similar or different. You see, each species would be capable of collecting nectar from many of the same plants that the other species visit. The difference in nectar types among the different plant species is what leads to the different tastes/types of honey. When the Apis species visit the same flowers, their honey is very similar. When they visit different flowers, their honey tastes different. It is perfectly reasonable for them to visit different flowers given their different body sizes. For example, Apis dorsata (the giant honey bee) is able to visit large flowers with deep nectaries as they have long tongues. On the other hand, Apis florea (the dwarf honey bee) is a very small honey bee and can visit flowers that are small. Thus, you can get these bees occurring in the same area but producing different honey.

Now, you could be asking about different subspecies of Apis mellifera. Given its large natural distribution, Apis mellifera has multiple subspecies (maybe around 30 or so). Some of those subspecies were brought to the U.S., where they are now managed as stocks of honey bees. For example, this would include Italian honey bees, Carniolan honey bees, etc. If you are asking if they make different honeys from one another, the answer is that it would be so minor that we would have trouble detecting the differences. Some of the subspecies have longer tongues than do the other subspecies. This would allow them to visit flowers with deeper nectaries. However, the floral visitation overlap would be so great that the honeys would be very similar. That said, you can have two colonies of honey bees in the same apiary produce slightly different honeys if one colony is primarily foraging on one species of plant and the second colony is foraging elsewhere, a scenario that is entirely possible.

If you are asking about bee species in general (rather than honey bees specifically), the bee species that make a honey-like substance include the honey bees, bumble bees, and stingless bees. The honey made by these three groups can be quite different, not only because they visit different flowers, but also because they process it differently. For example, stingless bee honey can have a very high moisture content, so it tends to be quite runny (and ferment quickly).

At the end of the day, the differences in honey tend to be due more to the floral source than the honey bee subspecies/species processing it.

Q  Refractometers and temperature

 I was looking for information on what the Brix reading really means when using a refractometer to determine moisture content in extracted honey. I have been taking Brix readings for years and appeared to have missed the necessary adjustment for temperature. I calibrate my refractometer using olive oil. I set it to 71.5 Brix. I take a Brix reading of my extracted honey. It says 81.5 Brix, but the temperature inside the honey area is 80°F. My refractometer states that the Brix reading is true at 68°F. I thought that the calibration using olive oil compensated for the temperature difference (80°F in the honey area vs 68°F true reading). Now, I think that I have to use a correction factor that will raise my Brix reading because of the higher temperature in my honey storage area. If this is true, does this mean that I must take the temperature of the extracted honey before I can determine the correct Brix reading or will room temperature suffice?

Aldon Maleckas
Michigan, August



Here is what I recommend doing. Place the honey to be sampled and the refractometer in the same room, at the same location, a few hours before you take the reading. Then, use room temperature in your Brix adjustment, given the honey and the refractometer should be at the same temperature. I will expand on this a bit for the benefit of the reader.

Refractometers are devices that are used to measure the amount of dissolved solids in a liquid. Beekeepers often use them to measure the amount of sugar (the solid) in honey (the liquid). The dissolved solids are called “Brix.” In our example, “Brix” would be interchangeable with “percent sugar.” We tend to want honey in the 15.5-18.5% water range. So, the opposite would be our desired Brix reading: 81.5-84.5% Brix.

As you note, temperature can greatly impact the accuracy of a refractometer. Thus, you need to know the temperature of your sample and the refractometer itself to ensure an accurate reading. A temperature conversion table accompanies all refractometers, or at least all that I have seen. Each refractometer is a little different so I would recommend paying close attention to the information that came with the model you have. The key, though, is to get the honey and refractometer to the same temperature so that you know which conversion to use. That is why I recommended setting the refractometer and honey in the same room, at the same temperature, before making the measurement.

I am glad that you own and use a refractometer. I feel that this is an indispensable piece of equipment to have, especially if you are going to produce and sell honey. They have really increased in availability and decreased in price over the years that I have kept bees. You can purchase one from nearly any beekeeping equipment supplier.

Q  Tunnels under wax cappings

This picture is the face of a honey frame. The odd pattern is a concern to me. Might you have any idea what it represents? Small hive beetles have decided that they need my yard in this region as a home. I worry that honey frames with this pattern have beetle larvae lodged below the surface.

Bob Baughman
Indiana, September


Great news: I do not think this is related to the tunneling activity of small hive beetle (SHB) larvae. I have never seen this sign as a visual indication of SHB infestation. Additional good news: I have two possible explanations of this for you.

The first explanation concerns a different tunneling insect, immature braulids (Family: Braulidae; Genus: Braula), also known as the bee louse. The bee louse is not really a louse at all, but rather is a wingless fly. There are multiple species of braulids, but the one most commonly discussed in the bee literature is Braula coeca.

This critter has a pretty amazing natural history. The adult bee louse lives on adult honey bees and it is nearly the same color and shape as a Varroa (though, as an insect, it only has six legs rather than eight like the Varroa). The louse feeds on secretions from the bees’ mouths, especially while one bee is feeding another bee. The adult braulid can even coerce the bee into regurgitating food by rubbing its feet on the adult bee’s mandibles. Crazy!

Braulids seem to prefer to live on queen honey bees, given queens are fed by workers a lot. I saw braulids on queen honey bees all the time when I was working on my Ph.D. in South Africa. I have never seen them in the U.S. My guess is that the acaricides we use to treat against Varroa kill the braulids as well, making them uncommon. I also think their general Varroa-like appearance makes them difficult for most people to recognize.

Braulid larvae are maggot-like. This makes sense given they are flies. The larvae live and develop underneath the cappings of honey cells. Their tunneling activity produces lines in the cappings, much like the lines you see in the image that you shared. I am happy to share that the bee louse does not negatively impact colonies, adult bees, brood, or even the queen. I have read quite a few papers on braulids and they seem, at worst, to be just minor nuisances. The lines in the cell cappings seem to be purely aesthetic. I wrote an article on braulids years ago. You can find it by Googling “EDIS honey bee louse” or by scanning the QR code here:

I shared that there is a second possible cause of the lines as well. Some bees cap cells slightly differently than do others. For example, some colonies produce “wet” cappings on honey cells while other ones produce “dry” cappings. This simply means that the capping either touches the honey below (hence, looking “wet”) or has an air pocket below it (looking “dry”). I think I read that bees can actually be selected for this trait. In the case of your comb, I have seen many colonies with ridges of all sorts constructed as part of the cell capping process. Thus, there is a possibility that the pattern you see is simply due to the capping pattern bees from that colony use. There is a reasonable probability that this is the cause, given the extensive patterns on the cappings in the picture you shared. When the tunneling is due to braulids, the lines are often longer and fewer. The sheer number on this frame keeps me from going “all in” on braulids. Regardless of the cause, be it braulids or just the unique capping pattern of the bees that compose this colony, I do not believe this represents a problem for your bees.

 Q  Who works the feeder?

 When a worker returns to the hive with nectar, she gives the nectar to a house bee who then stores the nectar and processes it into honey. What happens when I use an internal feeder filled with sugar syrup? Does this process still take place? When I look into the hive, it looks like a free-for-all. Is this still just the field bees collecting syrup and giving it to the house bees?

Ben Smith


Cool series of questions. The answer is that I do not know. ☺ I can say that with some confidence given that I have actually been asked this question before, a few times in fact. I always try to find a research-based answer every time the question is posed to me. I am sad to share that I have failed to find the answer in my multiple perusals of the literature.

That is not the end of the story! My team and I are interested in the same question for pollen patties. I have a sneaky suspicion that honey bees do not use pollen patties the way that we think they do. I suspect much of their attraction to pollen patties is related to the amount of sugar added to a pollen patty.

My team designed a study where we marked newly emerged bees and added them to colonies. We, then, placed pollen patties in the hives. The cool part about the study is that we checked the colonies daily to (1) see when marked bees would show up on the patties and (2) collect a subset of marked bees to determine what age cohorts of bees actually have pollen patties in their bodies.

What does this have to do with your question? Well, we needed a positive control for this study. In this case, we needed to use a patty of some type that we knew the bees would eat without hesitation. What type of patty would this be? One full of sugar, of course! Our positive controls were sugar patties. This is not the same as feeding bees sugar water in a feeder, but it provides the best opportunity that I know to answer your question.

We found that the worker bees visiting the sugar patties were not a random age. Yes, we found that workers of all ages would visit the sugar patty. However, we noticed that the number of marked bees on these sugar patties greatly increased when the bees were 15-25 days old, peaking around 19-21 days. This, of course, matches the onset of foraging. Either the bees were eating the sugar to gain the energy they need for foraging, or they were collecting the sugar because that is what foragers do — they collect sugar.

My guess (and it is just a guess) is that we would see a similar pattern of bees working sugar water administered directly to the hive. I suspect that bees of all ages would …