varroa mites

Video: Oxalic acid trickling

Here is a great little video that shows how to apply an oxalic acid trickle. It features Bee Craft Deputy Editor, Margaret Cowley (UK). She has the coolest little plastic squirt bottle that dispenses exactly 5 ml of the solution at a time. She just squeezes the bottle until the upper chamber is full, then she applies the measured amount into a seam of bees. After each seam, she refills the chamber and repeats.

The treatment is being applied on a December day with temperatures around 42-43 degrees F in a hive with one brood chamber and a super for winter. She treats the entire hive in a matter of moments—as fast as she can re-load the dispenser. Also of interest in this four-minute video is the cat and the woodpecker netting. (I love cats and never heard of woodpecker netting!)

Then too, Margaret cracks me up. As she trickles the solution, a little bee pops up between the frames and Margaret interrupts her narration to say, “hello.” So cute.

Be sure to enjoy.



  • Wow, that’s good stuff, I just wish I could go into a hive and have them “chilled” out like that. Here in Florida it seems they’re always ready to go!

  • I love the square hive, so the frames in the super are reversed! So, I wonder which month you would do this in Colorado?

    • Susan,

      It is applied to control varroa mites without using synthetic pesticides. Posts earlier in the week explained the whys and hows.

  • Thanks so much, this and your previous post about OAD are very helpful. I’ll definitely be trying that method this fall. I’ve seen everything from 30-50 ml as upper limit for dosage per colony, but I have 8-frame equipment, so that probably means applying closer to 30 ml?

    Also, I treated with Apiguard in mid-August last year because mite levels soared around that time. I would not feel comfortable waiting until December to treat. Would OAD in late fall work in conjunction with a late summer application of Apiguard? I was very happy with how that knocked mite levels way back, but I knew they weren’t going into January mite-free. Yet both colonies survived the winter and are doing well.

    • Virginia,

      Yes, I would say a knock-down in August with something like HopGuard or Thymol and then a mid-winter treatment with oxalic would be ideal.

      For 8-frame equipment, just don’t go above 5 ml per seam of bees and you will be safe. The maximum for a colony is 50 ml, even if that colony is in a nuc. Read the EPA label, if you are in doubt: the label is the final authority. It says, “The maximum dose is 50 ml per colony whether bees are in nucs, single, or multiple brood chambers.”

  • Hi,

    She makes it look easy, I will have to consider oxalic acid. Watching the video makes me more confident for trying it, thanks.

    In the end of the video, she puts back the supper with the frames at 90º to the brood chamber frames. It was probably due to the filming as in the beginning the frames were all aligned. But my question is, is this a problem? I did this the other day and only noticed later. I went back and put it right. But I wonder what would happen if I had left the super with the frames at 90º?

    Thank you for sharing the video.


  • That is a great video and a really neat squeeze bottle. Thanks for sharing. With this treatment being effective at lower temperatures that is of interest to me.

    I noticed the frame in the top super were orientated 90d to the frames in the brood chamber. That seems odd to me.

  • Can anyone advise me as a first time beekeeper if I can put down apiguard now in the spring on top of the brood box? I harvested honey in October. I believe I could harvest again but I think I’ll wait.
    I’ve had my hive right at a year now.

    If I do put apiguard down, can I still harvest honey in a month or so?

    Thank you for your help,


    • Janey,

      Harvest first, then use Apiguard. You don’t want to use it while honey supers are in place because the wax can absorb it. Follow the package directions for spring use.

  • Hi Rusty-I have ordered some Vivaldi boards, but can’t seem to find any ROUND Swienty feeders-just the square one. Do you/anyone reading the blog know of a source? Thanks so much-I appreciate it! Neat video

  • My friend has square boxes and he can also turn the frames 90 deg. He says his bees doesn’t care which way the frames are turned.

    PS. I live in Denmark

    • Henrik,

      I asked Margaret Cowley (in the video) about this. She said she usually puts the super on parallel to the brood frames, but she wasn’t thinking about it at the time the video was made. But she and I agree with you that it shouldn’t make any difference to the bees.

  • Rusty,

    Not sure whether you can help me (us) with top bar hives, but since the top bars do not have any space between them (unlike the Langstroths), it would not be possible to drip the oxalic acid solution from the top.

    Any suggestions from you or your followers?

    Thanks for your efforts on our (and our bees’) behalf, and for your excellent writing.


    • Daniel,

      I have one top-bar hive. For oxalic, I removed two bars from the end, spaced the bars so there was space between them, dripped the oxalic, pushed the top bars together, and returned the two end bars. It took a few minutes longer than the Langstroth but caused no problems.

  • Margaret is such a natural presenter, she speaks calmly and explains everything really well. Can see why they chose that hive to film, good as gold. Love the cat stalking in the background too.

  • Thanks for sharing. I’m trying this winter. When you played this you probably noticed putting the super back warm way onto the brood box set cold way?

    • Interesting study. But the pre-condition of no brood in the hive is not attainable in a large part of the world. Is it just because of mites in capped brood who are not reached by the treatment or is oxalic acid toxic for bee larva in uncapped cells?

  • Pedro,

    It’s been shown in studies that there’s no harm to brood with vapourising. I use it when required and if in the laying period, I’ll do three treatments 5-7days apart to cover the mites hatching cycle. I can only speak from my own experience but I have never seen dead brood or the queen stop laying.

    • Sean,
      Thank you so much for taking the time to answer my question. It is very useful to know!
      Where I have my (2) hives there is always some brood in the hive year round and now I will feel more comfortable trying it out.

  • I use a 60 ml plastic syringe (can be obtained from hospital/clinic worker friend). Can use any size syringe but 60 ml only needs to be filled once per colony. I attach a flexible IV cannula (no needle). You can also use flexible microtubing instead of the IV cannula if available. Hospitals/clinic often throw away outdated (albeit perfectly good) equipment and are happy to give it away. Fill the syringe to the desired maximum volume for the colony (for example, 50 ml). Insert the tip of the cannula over each seam and express the 5ml volume per seam. If filled to the correct volume at the start, no way to “overdose” the hive. Easy, quick, cheap.

  • It’s 45 F In Utah today. I want to do the dribble. I was talking to knowledgeable beekeeper (actually local inspector). He says he doesn’t do the dribble method, but would be worried the bees would eat it and it would hurt them? Rusty, can you help me weigh out the risks?

    • Kelsey,

      People were using the drip method for years and years before the vapor method, especially in Europe and South America. I’ve never heard of it being a problem except where it is used repeatedly during a short time span. Yes, they do eat it, but that is the beauty of oxalic acid. The acid is easily tolerated by honey bees (honey, for example, can be extremely acidic) but is not tolerated by mites. To me, this should be the least of your worries.

  • Is this treatment for mitigation of a known varroa infestation, or a “just in case” treatment of all hives?

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