Bald Brood

Greater wax moth adult.

Greater wax moth adult.

This image shows a section of a frame with a wax moth tunneling below sealed brood.  This symptom is called Bald Brood.

This image shows a section of a frame with a wax moth tunneling below sealed brood. This symptom is called Bald Brood.

An interesting brood symptom you may come across in a weak hive in the spring is Bald Brood. Bald brood is caused by the Lesser wax moth (Achroia gresella) or the Greater wax moth (Galleria mellonella.) You can see in the image below the linear pattern of uncapping that occurs due to the wax moths tunneling behavior. These symptoms can sometimes be confused as hygienic behavior; I have included an image showing some hygienic behavior of uncapping. One visible difference between hygienic behavior vs. bald brood is that there is no linear pattern of uncapping sealed brood with hygienic behavior. Colonies with bald brood often have raised sidewalls that are slightly above the other sealed brood, this symptom is not usually present when bees are uncapping larva/pupa associated with varroa, a lethal gene or another brood disease. I have seen these symptoms a handful of times over the past several years but in most cases the colonies were weak ranging from 3-6 Frames of bees. The best defense against wax moth is a strong colony. If you investigate cells near the ends of the linear pattern you can probably find the wax moth larva, look for perforations in the sealed cells. For more information on wax moth please see my previous wax moth blog here “Wax Mothor “Jennie’s blog on Wax moth damage”.

This image is cropped from the image above to give you a close up of what bald brood looks like.  You can see the raised cell walls around the uncapped pupa.  Also, note the darker brown convex sealed cells in between the open cells (convex but not normal looking.)  This was the path of the wax moth larva.  There is a perforation in the cell to the right of the last uncapped cell.  I found the wax moth in that perforated cell.  There is a photo of the wax moth larva below.

This image is cropped from the image above to give you a close up of what bald brood looks like. You can see the raised cell walls around the uncapped pupa. Also, note the darker brown convex sealed cells in between the open cells (convex but not normal looking.) This was the path of the wax moth larva. There is a perforation in the cell to the right of the last uncapped cell. I found the wax moth in that perforated cell. There is a photo of the wax moth larva below.

Wax moth larva that was removed from the perforated cell pictured above.

Wax moth larva that was removed from the perforated cell pictured above.

Bald brood is caused by the wax moth tunneling below the sealed brood.  Bees can detect something is wrong when the wax moth is tunneling below and start to uncap cells.

Bald brood is caused by the wax moth tunneling below the sealed brood. Bees can detect something is wrong when the wax moth is tunneling below and start to uncap cells.

This image shows the results of a hygienic test.  You can compare the edges of the open cells to the open cells in the bald brood image.  This image also shows how the hygienic bees will start to chew down and remove pupae and larvae.

This image shows the results of a hygienic test. You can compare the edges of the open cells to the open cells in the bald brood image. This image also shows how the hygienic bees will start to chew down and remove pupae and larvae.

This is an image of hygienic behavior.  The bees are uncapping and chewing down larvae because they detected varroa mite, a lethal gene or some other brood disease.  Note there is no real pattern to the uncapping.  Also note the pepperbox brood pattern.

This is an image of hygienic behavior. The bees are uncapping and chewing down larvae because they detected varroa mite, lethal gene or some other brood disease. Note there is no real pattern to the uncapping. Also note the pepperbox brood pattern.

One may confuse the linear uncapping for early stages of chalkbrood so I have included this image to compare to bald brood.

One may confuse the linear uncapping for early stages of chalkbrood so I have included this image to compare to bald brood.

In this image you can see hygienic behavior displayed in circled uncapped brood.  I also circled some other problems related to varroa mite.  You will see a few bees circled with Deformed Wing Virus (DWV.)

In this image you can see hygienic behavior displayed in circled uncapped brood. I also circled some other problems related to varroa mite. You will see a few bees circled with Deformed Wing Virus (DWV.)

Written By: Rob Snyder

Rob Snyder has written 58 post in this blog.

I currently work out of the Butte County Cooperative Extension in Oroville, CA as a Crop Protection Agent. I received my B.S. in biology from Delaware Valley College, PA. There I attained a majority of my entomological knowledge from Dr. Chris Tipping and Dr. Robert Berthold. After graduation, I was an apiary inspector for 2 years at the Department of Agriculture in Pennsylvania. In my third year there, I still inspected some colonies but I mainly focused on The Pennsylvania Native Bee Survey (PANBS) where I pinned, labeled, entered data and identified native bees to genus species. Leo Donavall assisted me in learning the basics on positive Identifications of the native bees. Around the same time I began working on coordinating kit construction and distribution for the APHIS National Honey Bee Survey. I was also fortunate to conduct many of these surveys with fellow co-worker Mike Andree and Nathan Rice of USDA/ARS throughout California. All of these experiences have led me to where I am today, working to assist beekeepers in maintaining genetic diverse colonies resistant to parasites while reducing the use of chemical treatments in colonies. The BIP Diagnostic Lab at the University of MD is in an integral part of this process by generating reports in which we can track change and report to beekeepers vital information in a timely manner which may influence their treatment decisions.

  • Laura Urban

    Rob – Can you clarify the difference between bald brood and hygienic behavior? It looks like in one post bald brood (the almost developed pupae that are still white with no capping) is attributed to wax moth larvae damage, while in another post it looks like it’s attributed to hygienic behavior. Or, is bald brood the tunnel left by the wax moth larvae and the uncapped pupae?

  • Rob Snyder

    Bald brood is caused by the wax moth tunneling below the sealed brood. Bees can detect something is wrong (How? Guesses: hygienic behavior,pheremones, or vibration?) when the wax moth is tunneling below and start to uncap cells. The bees let the pupa/larvae in the cells (usually survives to adult), with normal hygienic behavior they will start to remove pupa/larvae or start to chew them down (Shown in the hygienic photo). Sometimes the cap is perforated by the wax moth larva and the bees will uncap the brood. The symptoms shown in a colony with bald brood are different than a colony showing hygienic behavior for mites or other problems (Refer to images above).

    Bald brood symptoms can also be caused by workers not capping the cell all the way often leaving a small circular hole in the center of the cells. But with this you will see groups or patches of “bald brood” rather than linear patterns following wax moth tunnels.

  • http://bees.tennessee.edu/ Michael Wilson

    I believe you can see the raised rim around the uncapped pupae in VSH bees, in cases not necessarily associated with wax moth larvae. I’m pretty sure I’ve heard USDA Baton Rouge lab personnel noting this trait in their presentations before. I’ve seen the raised rims frequently in my VSH colonies too, and it can sometimes misleading look like uncapped drone pupae on first glance due to the raised nature of the rim. I think this is where they uncap, then don’t remove the pupae, then start to build it back, perhaps.

    Great pictures Rob, as usual!

  • http://cnn.com Mai

    Fantastic blog you have here but I was curious about if you knew of
    any message boards that cover the same topics talked about here?

    I’d really love to be a part of community where I can
    get responses from other knowledgeable people that
    share the same interest. If you have any recommendations, please let me know.
    Cheers!

    Feel free to visit my blog :: news 2 you (Mai)

  • http://buygreencoffeebeanextractonline.weebly.com/ where to buy green coffee bean extract

    Have you ever thought about writing an e-book or guest authoring on other sites?
    I have a blog centered on the same information you discuss and would really like to have you
    share some stories/information. I know my readers would value your
    work. If you are even remotely interested, feel free to shoot me an email.