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Thread: Varroa Control

  1. #1
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    Default Varroa Control

    I am an experienced beekeeper and consider I take good care of my bees, 5+ hives on the NW coast of Scotland and up to a few years ago the area was varroa free. Yesterday after a decent stretch of low temps I applied OA by sublimation, I do this every winter. The resulting 24hr drop was quite surprising given my regular monitoring and management of the dmd. Throughout the brood rearing period of the year I place the yellows under maybe every 4 weeks or so and chart the drop. I see the usual trends and suppress the varroa with icing sugar which has worked well. Going into this winter the dmd was 2/3 per day. Today after yesterday's sublimation I had some dmds up in the 90s and 70s, quite a surprise, other hives were up of course but in the expected range after a sublimation.
    I have been following Sussex Uni's recent papers on the use of OA and how sublimation is the best method of the three. If as I am lead to believe I have killed off ~97% of the phoretic varroa I am trying to calculate if and when I should apply another treatment in an attempt to remove as much as possible before the Q starts laying. Popular current thinking is ~6 days after first treatment and then 15/16 days after the second treatment which seems logical.

    Would anyone like to comment on the expected effectiveness and timing of this program.

    Thanks,

    M

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    Senior Member fatshark's Avatar
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    Hivemaker on the BKF has reported 3 treatments at 5 day intervals if brood is present. I think he determined this empirically. I suspect the level and availability of brood and the duration of the phoretic phase (which isn't constant) are likely to mean that no single answer is likely to be correct. I've used 3 x 5, 4 x 5 and multiple treatments with 4 or 5 day intervals. I've not aware any is better or worse. Daily mite drop falls off pretty quickly after a single treatment, so I'd not want to leave a 15/16 day gap ...

    The late summer/early autumn treatment is the most important as this is the one that hammers down the mite population before the winter bees are exposed to viruses.

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    It is really sad that people continue to take bees into previously Varroa-free areas. Anyway, you asked for comments on your plans.

    The timing between treatments - why not repeat twice (or more) at roughly 6 day intervals? Then you've covered a full cycle of sealed brood even if the queen is laying. A few of my crown boards have some detectable warmth so I think some colonies here are brooding. Of course, I can't recommend multiple sublimation, as the only legal way to treat is to use ApiBioxal according to the instructions, and they say sublimate only once per year. For OA treatments I just treat by the calendar rather than after cold weather. Daylength seems to have more influence on brooding than recent temperature and colonies will just briefly restart brood rearing at random times no matter what the weather.

    Your results are probably proof that icing sugar does not work as a Varroa control. There have been papers published on this. In much of the year most mites will be inside sealed cells and therefore immune to powdered sugar. Even those out of cells may not be affected. Some mites are firmly clamped on and lodged between abdominal segments so I doubt that a high proportion of them are susceptible to the icing sugar. Use it only to monitor mite levels, and monitoring that way is much better than looking for mite fall onto a sticky board ... and that is better than mite fall onto a dry board.

    Finally, the University of Sussex's study is just one study amongst many. Even that study doesn't report a significant difference for most parameters between trickling and sublimating. Colonies do seem stronger in spring after sublimating but they used a standard 50 ml for trickling which is significantly more than most of us would use - so it wasn't a fair comparison. However sublimation is a good method so no need to change now.

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    Administrator gavin's Avatar
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    Quote Originally Posted by fatshark View Post
    The late summer/early autumn treatment is the most important as this is the one that hammers down the mite population before the winter bees are exposed to viruses.
    Do you use sublimation for this too? Just considering my options ...

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    Senior Member fatshark's Avatar
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    Yes. For the last couple of years.

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    Quote Originally Posted by fatshark View Post
    Yes. For the last couple of years.
    Do you feel/know that this is more efficacious than Autumn Apiguard?

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    Senior Member fatshark's Avatar
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    No I don't. It's certainly 'good enough' and mite levels have been very low. However, I've done no side-by-side comparisons that would stand any sort of scrutiny.

    However, unlike Apiguard, OA (Api-Bioxal etc.) treatment by vaporisation does not seem to stop the queen from laying as it often does with Apiguard. Since treatment usually coincides with the important egg-laying for generating the winter bees I think this is a significant benefit.

    The other thing I have to consider is temperature. Having moved to balmy Fife in 2015 the autumn temperatures are sometimes borderline for Apiguard treatment after the summer honey is taken off. I don't currently take my bees to the heather, but once you're into September the likelihood of getting the necessary 15C for Apiguard is much less than it was when I was living in the Midlands.

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    Senior Member Jon's Avatar
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    This is a summary of Jennifer Berry's work re the futility of sugar dusting.

    Also, although the NBU recommend estimating mite levels by counting mites which drop through the mesh, my experience is that this is completely inaccurate.
    You don't see a mite for months then you get a massive drop when a treatment is applied.
    Sugar shake with a measured sample of 300 bees gives a fairly good estimate of mite levels.
    There is info onthe NIHBS site here

    Agree with Gavin re the LASI research. Very easy to find flaws in the methodology and even on their own results there is little or no difference between trickle and sublimation although the press releases do not reflect that reality.

    Look at the graph from the paper.
    Trickle at recommended dose kills 93.3% of mites
    Sublimation at recommended dose kills 93.1%

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    Senior Member fatshark's Avatar
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    At the highest doses in that paper there was no statistical difference between trickling, spraying and sublimation. I agree that the latter has been overhyped and many have ignored the absolute requirement for removal of sealed brood to achieve the 93+% levels they're reaching.

    My comments above were restricted to comparison between sublimation and Apiguard during the autumn.

    I agree that the estimates from natural mite drop are a bit hit and miss - it's only really any use after treatment has been applied.

    Finally, 50ml for trickling in midwinter may not be too far off for Sussex ... when I lived much further South it wasn't unusual to have 7-8 seams of bees in strong colonies in early January. What is known is that trickling is not good for unsealed brood ...

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    Thanks for all the helpful responses, I will take them into account. My inclination now after receiving other inputs is to conduct another sublimation 6 days after first, with a third again 6 days on again.

    M

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