What is that Smell?…American Foulbrood!

AFB brown larvae

“Coffee” brown larvae

Three summers ago I was hired as a Pennsylvania Apiary Inspector. When I started this job I thought back to my mentor Dr. Robert Berthold. He taught us bee diseases and pest by showing slides and using key descriptive words. This inspired me to start photographing various diseases and pest found inside and outside of the hive. Over the next few weeks I will share my experience with some of these diseases and pest. I chose American Foulbrood (AFB) first since it’s the most notable brood disease.

So I first thought to myself…How does AFB spread? America Foulbrood is introduced to the hive by drifting bees from nearby colonies, infected equipment/tools, beekeepers and robbing. The infection begins when spores are introduced to the hive. Nurse bees will feed larvae food contaminated with spores. Once spores are in the midgut the vegetative form of the bacterium takes over using the larvae as a source of nourishment. After the cells are sealed, death occurs. If death occurs while in the pupal stage, there will be a protruding tongue present. When there is a high infection you can notice moisture on cappings as they start to sink. Sunken capped cells are a result of larvae decomposing and sinking into the cell.


Sunken Cappings with perforations are a good indicator of AFB

The first time I saw this disease it was unforgettable, I had gotten a call from a beekeeper concerned that he had this disease. I drove to the apiary with the suspect AFB hive. I noticed a strong odor walking into the apiary. The odor reminded me of rotting meat. I then Inspected 3 of the 4 hives leaving the AFB suspect last. The three prior to the last were clean. When I cracked the lid on the last hive I immediately smelled the same odor I noticed on the walk in. Upon further investigation I found “coffee” brown larvae that were melted down to the bottom of the cell. I also noted a “spotty” brood pattern along with sunken cappings with perforations in them. I then performed the “rope test” followed by the Holst milk test and confirmed this was American foulbrood. I then took samples into sterile containers to test for the Terramycin resistant AFB.

It turned out that the beekeeper was treating with Terramycin and the symptoms came back each year. This indicated the AFB strain was Terramycin resistant and lab test confirmed this theory. I recommended the beekeeper to burn the hive. I let him know about the treatment Tylan but warned him about the residuals of this chemical left behind in the hive since Pennsylvania does not have a burn policy on AFB. He had decided to burn the hive. It was a great experience but also a little disheartening knowing you have to inform the beekeeper of this notable disease.

Deadout Colony with AFB

Deadout Colony with AFB


AFB "rope" test

AFB “rope” test

Written By: Rob Snyder

Rob Snyder has written 66 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.


12 Responses to “What is that Smell?…American Foulbrood!”

  1. Elizabeth Chrissian

    Live in FL. Sure there are bees around. Want to train a male Golden Retriever to scent for American, European Foulbrood & other bee diseases & bacteria that might have odor. Goal is to have a convenient quick way to detect the possibility of a hive infection before it becomes unmanageable & spreads. My end reward is to have a small income.
    To train the dog I need scientifically collected scent samples, clearly marked, & packaged.
    I understand they do this in Australia & it has proven an invaluable & quick method of discovery & subsequen control of bee hive maladies. Plz advise where I might obtain samples of scent for the aforementioned reasons. Thank you..

  2. Jill McLeod

    I want to ask a question on another topic actually :/

  3. Jill McLeod

    Um the topic is the flatulent smell which I think is emanating from the hive in my ceiling (which I’ve wanted desperately yo keep!)