varroa mites

What is guanine?

After my last post, many people wanted to know “What the heck is guanine?” Very simply, guanine is one of the four nitrogen-containing bases found in DNA. You’ve probably seen strings of letters representing DNA structure that look something like this: ATGGATGTCGACGGT and so on. The four letters represent the four bases: adenine, cytosine, guanine, and thymine.

However, that is more than you need to know for beekeeping purposes. It just so happens that the excrement of Varroa mites contains about 95% guanine. Guanine so pure shows up as a bright white glob—a deposit the mites leave on the inside of brood cells. After all, there are no “facilities” for them to use while they are locked under a capping, squeezed between a bee pupa and a wall of wax, so they leave it where they are.

Mite feces

Mite feces. Photo USDA-ARS.

If you find that your empty brood cells are loaded with irregular white deposits, it is a sure sign of a heavy mite infestation. If you hold a frame up to the light with the sun at your back, the deposits are especially easy to see. They are usually found in the top of the cell, so rotate the top of the frame away from you for easiest viewing.

The best part about guanine is its name. Guanine was first discovered in bat and bird excrement, a substance known as guano. In 1850, when scientists were able to isolate this white chemical from the rest of the stuff in the droppings, they named it guanine. How dainty.

Luckily for beekeepers, mites and bats and birds have something in common—a lot of guanine in their poop, a fact that lets us know who has been hanging around and where. The photo shows an adult mite in a brood cell amid lots of excrement. A mite is one of those things I would rather not be.



  • How very interesting! I wonder if this is the white substance I sometimes see when melting beeswax cappings.

  • Rusty,

    I have occasionally seen workers carrying a white glob, about the size of a pellet of pollen, usually around the edge of the brood box I’m inspecting. (Will try to get a picture). Are they be cleaning it out of the comb?

    Time to take some pictures of frames and do a mite scan on computer. Digital photography is SO useful to beekeepers. Thanks!
    Shady Grove Farm
    Corinth, KY

    • Nancy,

      I’ve never seen that, but bees do clean out the brood cells so it is possible. I would love to see a pic if you can get one.

  • I thought the bee larvae pooped before spinning its cocoon. Is none of that “junk” at the bottom of the cell bee larvae poop?

    • Hi Karen,

      I’m not sure I understand your question. Bee larvae do indeed poop at the end of the larval stage just before they spin a cocoon, so some of the junk at the bottom of the cell is bee poop. But bee larval poop is dark, not bright white like mite poop.

  • I have found an excellent organic product to help bees fight off varroa and I am using it with great success with my bees. My bees were infested with varroa, there were great numbers outside the hive with deformed wings, dying in great numbers. But I could not see any varroa inside the hive or on the bees.

    I practice natural beekeeping and my research on the Internet led me to Hiveclean, an entirely organic product made of citric, oxalyc acids and essential oils, used by organic beekeepers in Austria. It does not kill the varroa, it changes the acidity of the hive. The varroa does not like it and leaves the hive by dropping through the varroa mesh floor at the bottom, where it is caught on sticky paper and cannot go back up. I had hundreds of mites on the paper the day after I treated my bees for the first time. Gradually, the number of mites dropped and I have hardly any bees with deformed wings outside the hive. Because the substance is sweet and a bit sticky, it also encourages the bees to groom themselves. I treated the bees once a week and it took 2 months to bring the problem to an acceptable level. If I hadn’t treated my bees, I have no doubt I would have lost them. I continue to treat them regularly.

    The product can be bought from It is very easy to use. Because I don’t use a queen excluder, I had brood in the first super as well as in the brood box and I treated the bees in the first super as well as in the brood box and I am sure it made a difference too.

    I am based in England, West Sussex. I hope this will be useful to other beekeepers.

    • Chantal,

      I’ve heard good reports about Hiveclean, but I don’t think we can get it in the states, probably because it contains oxalic acid, a chemical not approved for use in bee hives here.

    • Chantal,

      Here’s my theory: In the US we have a long registration process for things such as insecticides. Application for registration must be accompanied by extensive testing, all of which is conducted and paid for by the manufacturer who stands to make money once the chemical gets approval. With a chemical like oxalic acid which is cheap and readily available at your local hardware store, no one stands to make a lot of money from it, so no one wants to pay for testing protocols, so no one is applying for registration.

  • In England, oxalic acid is routinely applied in the week between Christmas & New Year, on a fine day. It is deadly to brood, as well as the mites, but there’s little at that time of year, so not too much damage done. It is trickled along the seams.

    • John,

      That’s a good way to remember the best time to apply. I will make a note of that. I usually think “winter solstice” which is pretty close . . . just a few days earlier.

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