feeding bees

AFB-fortified pollen

­­­Oops. Unfortunately, bee-collected pollen can transmit the spores of American foulbrood just like honey. It works like this:

A colony of bees has become infected with the bacterium that causes AFB. The disease only affects young larvae less than 48 hours old, but adult bees can inadvertently carry the spores throughout the hive.

When a diseased larva dies in its cell, it can release as many as 2.5 billion spores. A nurse bee attends to the mess, cleaning up the dead larva and polishing the cell. But as she works, many of those spores stick to her body and she swallows even more.

In the cramped confines of the hive, she rubs against other bees including a forager who is unloading her pollen into an empty cell. Millions of spores are transferred to the hairs on the forager’s body. Once her pollen is unloaded, she heads back out into the field and begins to collect more.

As the forager sweeps the pollen off her body and into her pollen baskets, spores of AFB are whisked along with it. The spores adhere to the sticky pollen and become embedded in the pellet. These are not wimpy spores—they can survive in bee equipment for forty years or more.

When her pollen baskets are fully loaded, the forager returns to the hive where Beekeeper A has installed a pollen trap. She squeezes though the trap and loses one of her pellets. It drops into the collection drawer below. Damn.

Undaunted, the forager unloads the remaining pellet, gets some food from one of the nurses, rubs against a few others, and is out the door again.

Towards evening, Beekeeper A unloads the pollen trap, dumps the pollen in a plastic bag, and sticks it in the freezer. But freezing is no match for those AFB spores; they are still completely viable when Beekeeper A sells his pellets to the health food store where they are repackaged and dropped in another freezer.

Next month, along comes Beekeeper B. Beekeeper B wants the very best for his bees, so he buys pure, natural, bee-collected pollen to supplement his colony. Ouch. Spendy. But he buys it anyway. He takes it home, crushes the pellets with a mortar and pestle, and feeds them to his bees.

The bees love the stuff, frolic in it, and carry back to their hive along with a few million spores of AFB. By spring the colony is dead, smelling rotten, and the hive needs to be burned. Beekeeper B can’t figure out what he did wrong. . . .


Bee-collected pollen. Photo by Lamiot.

Fortunately, bee-collected pollen can be irradiated to neutralize the AFB spores. Once irradiated, it may be fed directly to bees or mixed into pollen substitutes.

In addition to AFB, pollen may also carry chalkbrood spores. To be on the safe side, never feed pollen to your bees unless you know the source of the pollen is disease free. The best way to do that, of course, is to trap pollen from your own disease-free hives.

Commercial pollen packaged to feed bees is usually irradiated, but pollen from health food stores and similar establishments probably is not, so be a careful consumer, read the label, and ask questions. In most cases, your bees didn’t need the extra pollen anyway, so it is a sad mistake to make.


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  • Thanks for this description of how AFB can spread to healthy hives. The University of Minnesota tested the viability of AFB spores in equipment that was 99 years old and found it was just as deadly as it was at 40 years old. Nice to know irradiation kills the spores in pollen. I wonder if anyone has tried to irradiate spore-laden woodenware to see if that is an effective alternative to burn and bury.

  • Wow!! Makes you think twice about trying to help so much. Maybe we should just let nature do what it does best and trust that it knows what its doing.

  • Rusty,

    Interesting – I was aware of honey as a potential source of infection, but I had not considered pollen. You say that diseased larvae can release 2.5 billion spores (= 2,500 British billion). An article on AFB published (undaated) by Florida Department of Agriculture and Consumer Service gives a much lower figure of 100 million spores. It also says that AFB spores can remain viable for more than 70 years in honey and beekeeping equipment, whereas JoAnne quotes 99 years. (https://view.officeapps.live.com/op/view.aspx?src=http%3A%2F%2Fentnemdept.ufl.edu%2Fhoneybee%2Ffiles%2Fspeaker_notes%2Fdave_AFB%2520outline.doc)
    It is academic – infected larvae produce a lot of spores that remain viable for many years! However, I wonder why there are these different figures. I would be interested in seeing the source of the University of Minnesota study.

    • Brian,

      Here’s yet another study that says “over one billion” spores can be released by one larva. I’m sure it depends on how the studies are done, how sensitive the equipment, and the methods used. I agree with you, the bottom line is “a lot.”

    • Brian, the test result (will woodenware infected with AFB 99 years ago still kill a colony of bees=yes) was shared in one of our MHBA (Minnesota Hobby Beekeeper Association) monthly meetings by Gary Reuter who works with Marla Spivak. I will ask him if the study was published and post here if there is a link to it.

  • Great information, especially since im still learning. When I eventually collect the pollen from my own bees, how can I irradiate it myself??

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