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  "description": "Miticides kill Varroa. They also have detrimental side effects for the brood, workers, drones, and queen. Some of these side effects are more damaging than others, but many can be avoided (or at least mitigated) with proper colony management.",
  "path": "/miti-side-effects/",
  "publishedAt": "2026-05-29T16:00:16.000Z",
  "site": "https://theapiarist.org",
  "tags": [
    "acaricides",
    "Norroa™️",
    "Rational Varroa controlSuccessful Varroa control involves understanding that when you treat is probably more important than what you treat with.The ApiaristDavid (The Apiarist)",
    "Rational Varroa control",
    "Subscribe now"
  ],
  "textContent": "I made the comment last week that all unexplained colony losses are due to _Varroa_ , unless there's unequivocal evidence they are due to something else.\n\nIf there are three weeks of rain in November, the stream floods, and you watch impotently as your hives are washed away downstream, I'll grudgingly accept that _Varroa_ wasn't to blame.\n\nHowever, 'unexplained' losses, in particular the majority of winter losses, are likely due to the detrimental effect of mites and the viruses they transmit within the colony.\n\nThis is why I stress that mite management — minimising the mite numbers in the colony — is such an important component of beekeeping.\n\nSome beekeepers appear to be able to achieve this without the use of chemicals, but for most bees and most beekeepers it involves the correct use and application of miticides {{1}}.\n\nMiticides — literally mite killers — are chemicals administered to kill mites and reduce their number in the hive below an acceptable threshold. Because _Varroa_ mites are members of the _Acari_ subclass of the Arachnids, along with ticks, these chemicals are sometimes termed acaricides.\n\nThe only good mite is a dead mite.\n\n## Regulatory approval\n\nMites, like ticks and bees and beekeepers, are living things, and so share many basic physiological and biochemical processes.\n\nTo receive regulatory approval, the _benefits_ of the miticide must outweigh the _risks_ associated with its use. Typically, those risks would be for the bees — that is, the host organism — or the beekeeper, but they could also include environmental risks {{2}}.\n\nA miticide may be very effective at killing _Varroa_ , but if it were highly toxic to humans by trace level contact, it would not be approved.\n\nAlthough many _products_ have received regulatory approval, the range of _active ingredients_ (_i.e._ the chemical constituent that kills the mites) they contain are disappointingly limited.\n\nThis post is only available to paid sponsors of __The Apiarist__. Sponsors get more … posts, news, and information on the science, art, and practice of sustainable beekeeping. They also have access to over a decade of legacy posts, and ensure __The Apiarist__ continues to appear every week.\n\nSign up as a sponsor\n\nThere are numerous formulations, some involving combinations, but all belong to one of three types of _organic_ chemicals (formic acid, oxalic acid, thymol), or one of three types of _synthetic_ chemicals (pyrethroids, organophosphothionates, and formamidines).\n\n❗\n\nI'm excluding Norroa™️, the recent RNAi-based therapy, from this post. Firstly, it's too new for there to be sufficient information on side effects after long-term usage. Secondly, it's not actually a miti****cide****. It suppresses mite reproduction, but __does not kill__ the mites. RNAi-based therapies are highly specific, but there's good evidence from other systems that resistance can occur. Time will tell whether this is also true for Norroa™️.\n\nAlmost all approved miticides will kill 90 to 95% of Varroa if used appropriately. In this case, “appropriately” means when administered in the right way, at the right dose, and at the right time.\n\nRational Varroa controlSuccessful Varroa control involves understanding that when you treat is probably more important than what you treat with.The ApiaristDavid (The Apiarist)\n\nOf these, at least in terms of benefits to the colony, timing is probably the most important. The right dose at the wrong time might be ineffective as far as preventing overwinter colony loss. I've discussed this at length in a previous post titled “Rational Varroa control”.\n\nIf used in a manner that kills 90-95% of the mites, _timing_ is much more important than the particular miticide used.\n\nTherefore, it makes sense to take other factors into account when choosing which miticide to use; cost, availability, ease of administration … and the side effects associated with its use.\n\nAnd there _will_ be side effects.\n\n### This post is for subscribers only\n\nBecome a member to get access to all content\n\nSubscribe now",
  "title": "Miti-side-effects",
  "updatedAt": "2026-05-29T18:00:16.921Z"
}