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A fight with the varroa mite in New Zealand

Varroa destructor hit the North Island first. It established around Auckland and spread gradually south. At first, beekeepers negotiated quarantine lines. Some apiaries were split down the middle, and boundaries had to be renegotiated every time the infestation spread. And in the meantime, an infested feral colony rode a hollow log into Wellington and Frank’s bees became the first in the area with Varroa.

Frank did not shy from the “bad beekeeping” stigma that encourages beekeepers to under-report cases like this. Instead, he worked to contain the infestation. He marked a five-mile radius around the Varroa hive, determined to destroy neighboring colonies to prevent Varroa from spreading. Frank climbed fences, turned ankles, and plugged and poisoned the wild beehives inside his quarantine zone. He offered honey to people who could point him towards feral colonies. He even managed to poison a nearby beekeeper’s unregistered hives—by mistake, of course—he had thought they were abandoned.

Frank got most of the ferals. All but one colony, actually, because it was on private property and the owners would not grant him access. So Varroa proliferated in the Wellington area, expanding outwards as the northern population spread south. The quarantine was a losing battle, Frank says.

That’s part of what makes Frank’s effort so admirable. Facing an impossible task, he refused to give up. These days, in anticipation of miticide resistance, he is exploring alternative Varroa treatments. In order to monitor mite levels, Frank  “fogs” his hives with vaporized food-grade mineral oil (FGMO) using a small flamethrower. He shows me how to pump a few puffs into the front entrance of each hive and warns me not to place the fogger too close. The popcorn sound is bees cooking, he says. Overall, casualties are relatively low. Frank estimates that we’re singeing the wings of approximately twenty bees per hive. After fogging the first apiary, I am red-faced and dizzy. Frank mentions that a dusk-mask would be advisable.

The fog agitates the mites, providing a one-day knock down, but it does not kill them. We collect the mite fall on slide-out “sticky boards” on the floor of each hive. These help us determine whether to implement a follow-up cord treatment. The short cotton cords are soaked in a solution of equal parts honey (or sugar syrup), food-grade mineral oil, and beeswax, adding 5% thymol for extra effect. Once dry, they are placed on top of the frames, two cords per brood box. The honey attracts the bees to the cords, and the FGMO kills the mites. Frank treats with cords about once a month, as needed.

These techniques were developed by Dr. Pedro Rodriguez of the United States, but Frank is experimenting with them himself to determine which treatments work best for his bees. It’s extra work for uncertain payoff. That’s some admirable beekeeping.


Frank uses a wide-tooth shearing comb to check drone brood for mites.

Fogging the hives with food grade mineral oil.

Cotton cord soaked in honey, mineral oil, beeswax, and thymol.


    • He marked the five-mile radius because that’s the distance a bee can reasonably forage or swarm. Then, after destroying his own Varroa-ridden hives, he tried to destroy all the feral colonies in that radius because any of them could be carrying Varroa.

      If you think about it, his own bees probably picked up the mites from feral bees (from flower-sharing or drifting, for example) and then, after his hives became infected, some of them would have swarmed, becoming feral colonies themselves, and taken the Varroa with them. By destroying all the feral colonies he was trying to keep that five-mile radius Varroa-free. There would be no way to do that without first destroying every single feral colony within that radius. As it turned out, the one he was not allowed to destroy is likely the one that re-infected the entire region.

  • Oh. Ok, thanks. That makes some sense. I missed the part about him destroying his own hives too. Man, that was/is heart-breaking. For us all. 🙁

  • He should be totally our hero for facing the problem and doing what must have been heartbreakingly painful, destroying so much of what he loved to save the rest. And the individual who would not cooperate probably lost his hives as well. OK, it was a feral colony, so he lost his pollinators anyway. I think a lot of us would really like to hear followup about the cord treatment, and I wish Maggie will send Frank our best wishes!

  • Wonder if anyone has tried using a ULV (Ultra Low Volume) sprayer to deliver the FGMO. Would reduce heat related mortality. We use them in pest control to treat voids, and I expect the oil would spread very well. We never use heat based foggers any longer.

  • Rusty, you’re exactly right. Frank destroyed surrounding colonies (including his own) to keep them from sharing and spreading Varroa. Nancy, I will talk to Frank about cord treatment followup. I think he’s been doing it for a few years. And, of course, I will link him to this page. I’m sure he appreciates your support.

  • Sounds interesting. I would try the cording in my hives, but I’m fascinated by the question of how the food grade mineral oil kills a mite. Does it poison, suffocate, make life slippery for it? Or am I missing something…


    • I’m not sure how the mineral oil kills mites but I’ve read a least three theories: 1) it suffocates them 2) it interferes with their sensory perception so they can’t locate brood cells in which to reproduce, and 3) it interferes with the reproductive process itself. I know that people use mineral oil for ear mites in cats. It probably works the same way, so if we could just figure that out . . .

  • Sounds as if we could have a breakthrough in mite control, although there will be as many schools of opinion as already exist for the dusting with sugar method. This doesn’t seem to be something a mite would develop a resistance to. How wet with oil would the cotton need to be I wonder…

  • I rely heavily on propagating colonies that can live in harmony with varroa and not trying to use new pesticides and antibiotics in an insect nest. Eradicating feral colonies happens in the USA every year. I personally feel this is a very bad idea. By eliminating these valuable specimens, we are shrinking the genetic volume we have to repopulate our own bee genetic pool. The mass shipping of bees in migratory beekeeping on a world wide scale has spread varroa and other problems to nearly every corner of the globe, Australia being the only place on earth where varroa is not currently found. But as this story shows, it will only be a matter of time. We need to raise more colonies that can detect infected brood and eliminate them, have heavier grooming capacity, propolize heavier, and adapt quickly to invasions from foreign intruders. Varroa is a difficult problem for most domestic bee colonies, but tropilaelaps are by far worse and may also be on our horizon….

  • Rusty, is thymol oil and thyme oil the same/interchangeable for the purpose of FGMO fogging? Do you know a reliable source for 5% thymol oil?

    • Terry,

      I would not substitute them for FGMO unless someone has recommended it. If I were going to experiment, I would only try it on one hive at a time. This sounds iffy. No, I don’t offhand know source for 5% thymol.

  • Studies have been conducted in New Zealand using psuedoscorpions for varroa mite control. They look like scorpions without tails and stingers just a lot smaller, smaller than mosquitos. They naturally live in soil but can be purchased. They are everwhere. A new species was recently found in wv and is the largest of species but still far too small to harm a bee.

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