|AFB Rope Test - note the color, when the diseased larvae is a milk chocolate color is the best time to do the rope test. AFB will rope an inch of more.|
American Foulbrood is something that can sneak up on a beekeeper. Most beekeepers have never had AFB before and do not know what it looks like. The times that I have seen AFB is usually when a beekeeper calls me and tells me their hives keep dying by early fall. I have them bring me one of their brood boxes of a hive that died. A quick inspection by and experienced beekeeper can see the AFB scale in the cells on the frames.
When I say experienced beekeeper, it is a beekeeper who has had AFB before and has fixed their hives. There are many long time beekeepers who have never had or experienced AFB. So, without getting burned by this disease, many beekeepers don't know what it looks like.
Personally when I was a young beekeeper, I purchased some used equipment. Unbeknownst to me, The used equipment was full of American Foulbrood scale in the frames. After getting AFB in many of my hives and then fixing the aftermath of the disease, the life of hard knocks gave me the experience to identify the disease.
Beekeepers tend to focus on an odor to troubleshoot for AFB. By the time and odor becomes an issue in the AFB hive, the AFB can become widespread in the hive and possibly have been spread to other hives. This is not an effective way to find AFB. AFB is a brood disease affecting older larvae. Young larvae will look fine. Older larvae will start to turn yellow. The larvae will start to darken to a milk chocolate color and turn to a gelatinous mass, that will flatten out into the bottom of the cell. The tongues of the diseased larvae usually sticks up in the cell off the bottom of the cell. This gelatinous mass will dry out and form a hard scale on the bottom of the cell. The scale is highly infectious. Bees do not have the ability to remove the scale. One frame of AFB scale has enough spores to infect every colony in North America. Millions of AFB spores could be in the scale on one frame. While this would never happen, I just wanted to mention the scope of possible infection. AFB scale is still infectious even after over one hundred years.
When the larvae is in the chocolate color stage, that is the time when the rope test should be administered. Poking the larvae with a small twig and slowly pull it away from the larvae. If the goo pulls out in a rope that is over an inch long that is probably AFB. If it does not rope an inch or more, it would not be AFB.
Normally American Foulbrood is not widespread. AFB usually gets spread from used equipment, bees robbing out a dying AFB colony, or from feeding store bought honey to your bees. There is a possibility that AFB spores could get into extracted honey. While this has no effects on humans, bees can come possibly down with the disease from store bought honey.
If your colony has larvae that is nice and pearly glistening white then your bees are fine. Whenever the larvae is discolored then there is a brood disease. The common brood diseases we see are chalkbrood (no treatment available), European Foulbrood Brood (Terramyacin treatment), The Crud (Terramycin treatment), American Foulbrood (remove diseased comb and burn frames, shake bees onto new equipment, treat with Terramyacin). If diseased AFB frames are not removed from the hive, the disease will start up again.
Learning to spot a disease is part of being a good beekeeper. Sometimes you may need help identifying a disease and there are beekeepers out there willing to look at your frames. You need to go through a veternarian to get a prescription for Terramyacin.