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Thread: 2011 varroa levels

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    Senior Member Jon's Avatar
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    Default 2011 varroa levels

    I started treating colonies around mid August with Apiguard and have seen hardly any mites dropping. Other years I have had a drop of 150 in the first 24 hours from some colonies. This year I am seeing just a few mites on the boards I have examined.
    Anyone else seeing lower than usual varroa levels? Last season's treatment was Apiguard in September and Oxalic in December.
    Last edited by Jon; 25-02-2012 at 08:12 AM.

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    Administrator gavin's Avatar
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    Had been going to leave the smaller colonies still down here, but I'm now persuaded to treat (Apiguard) having seen the thymol-induced knock-down on a friend's colony that hadn't been dropping mites without treatment. The stronger ones in the hills pose a bit of a problem as they cannot be treated yet - maybe in a week or so.

    Does your paucity of mites also apply to the big booming colonies that raised lots of drones?

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    Just started treatment. Last year used Apiguard and Oxalic. This year so far the natural drop has been very low but I treated with Thymol Crystals in alcohol anyway and after a week counted only 30 mites but will treat again with Oxalic in December. Our club apairy colonies which have been treated with Bayvarol strips have had a low drop as well. Where are all the varroa?

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    Senior Member Jon's Avatar
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    Quote Originally Posted by gavin View Post
    Does your paucity of mites also apply to the big booming colonies that raised lots of drones?
    I am not seeing significant numbers of mites in any colony, just like Jimbo's observations, only a few dozen here or there after treatment has started.

    Quote Originally Posted by Jimbo View Post
    Where are all the varroa?
    That's what I was wondering.
    I don't like to tempt fate but my bees have been really healthy and vigorous all year.
    Maybe we started with very low levels of varroa due to the effectiveness of Oxalic and that severe cold spell.
    Colonies must have been 100% broodless for quite a while.
    Last edited by Jon; 04-09-2011 at 03:13 PM.

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    Senior Member Adam's Avatar
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    Low mite levels for me too. I treated with Apiguard at this time last year and Oxalic Acid between Christmas and New Year. Just before treatment last year I did see some deformed wings indicating that the varroa were starting to have a deleterious effect on bee health. This year I have seen just one bee with deformed wings.

    I had external inspections from the bee inspector and also for my General Husbandry certificate this year and comments from both visitors that they were 'pleasantly' surprised that there were no varroa in the drones that were ripped out.

    For you guys further North than me with a longer broodless period in winter, Oxalic Acid should be a more effective treatment than it is for us Southerners.

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    Senior Member Jon's Avatar
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    Oxalic Acid should be a more effective treatment than it is for us Southerners.
    And it costs under 10p to treat a colony whereas other treatments such as Apiguard, Apistan and Bayvarol cost over £3.

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    mixed bag here. I've had my "best" colony really struggle with varroa this year. My best (non honey producers) have been swarms that have been treated with OA before they established brood.

    As an ongoing, low cost treatment, I think I disagree with Jon about icing sugar. I think it has its place, is effective in isolation and if you understand its weaknesses. It is not a replacement for thymol or oxalic acid nor is it a treatment to be used in isolation, but I feel that it is not to be discounted either.

    All that aside I have to say that our varroa levels have been a mixed bag, if you run an apiary with other people you MUST run treatments at the same time, agree an IPM and so on. There is no point putting OA on one swarm and not on another, putting Icing sugar on some and not others.

    I..We've screwed up this year, we both have bees that are struggling with varroa. If there's a plus side, we've identified the colonies not to raise queens from. We've tried, as much as possible to be hands off, while still treating, and we're obviously not doing enough.

    I still recall gavin's post from two years ago and I have bees from that queen so it remains a possibility, but we all take queens from survivors?

    Varroa are evil little buggers, you can play, you can try not treating, or just treating enough, but it's a sad, sad sight to see a colony struggling for the sake if having given them a dose of OA. I have bees in the latter. If they live I'll requeen them in the spring but I failed, I made a colony suffer because I knew better and that does make me hurt. I know it's a box of bugs but it pains me to see them struggle when I could, should have sorted them out when I had the chance.

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    Administrator gavin's Avatar
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    Quote Originally Posted by Nellie View Post
    I still recall gavin's post from two years ago and I have bees from that queen so it remains a possibility, but we all take queens from survivors?
    I'm touched! I remember it too. We probably all have pieces of that jigsaw in our bees. Varroa Sensitive Hygiene (excavation of infested brood), grooming and biting of mites, and other things that give resistance.

    As for powdered sugar, well, it will knock down some mites but however appealing the method sounds it is of very low efficacy. Those beginners who are being encouraged to adopt it as a main treatment are heading for the loss of their bees and that is sad and unnecessary.

    Varroa increase -


    Approximate monthly increase in worker brood during the active season: 100%

    Approximate monthly increase in drone brood during the active season: 300%?

    Against which there will be a small natural mortality rate, and maybe a larger one imposed by some bees.

    Varroa decrease with powdered sugar -

    Mites protected in sealed cells during treatment: 70%? (Guessing)
    Knock-down rate of mites on adult bees: 30% (Real data, many are clamped on)
    Mites lost on each sugar treatment: 30% x 30% = 9%

    So, if that is anywhere near right, even *weekly* powdered sugar treatments (and who can manage that) can't keep up with the expected multiplication rate. The Ellis et al study showed that fortnightly treatment made little difference to the mite build-up.

    *Maybe* if you have bees that are resisting the mite themselves, or some other factor is suppressing their build-up, that small help that powdered sugar gives matters. But usually it will not.

    This year Jon could have been trying dowsing round his apiary (it disorientates mites, don't you know, and they fall off onto or through the floor!) and would have shown that it is effective as a Varroa treatment because of his low levels. Point me to proper controlled trials that show that the effect of powdered sugar is good enough to hold mite populations down and I'll listen. Tell me of folk that tried it and say that it seemed to work for them, and I'll keep telling folk that 9% efficacy is not enough.

    Feel free to come up with a better figure than 9% if you can.

    Gavin
    Last edited by gavin; 09-09-2011 at 09:06 AM.

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    Senior Member Jon's Avatar
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    This year Jon could have been trying dowsing round his apiary (it disorientates mites, don't you know, and they fall off onto or through the floor!)
    Nah! I'm going to make an effigy with a willow twitcher in the scary form of Roger Patterson and that should drive the mites from my colonies like the rats from Hamlyn.
    Might even give it a penny whistle.

    Nellie, I still believe icing sugar is placebo - makes the beekeeper feel good due to being proactive.

    Gavin, I have always read that 80% of mites are under cappings at any given time so your estimate should maybe be nearer 6% than 9%.
    Last edited by Jon; 09-09-2011 at 10:16 AM.

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    I treated this year 8 colonies with thymol mix. Very low drop before - (under 2/day) from each hive: during treatment less than 20/day. Last year my 2 colonies had hundreds drop.

    Did not use oxalic acid in winter, no sugar icing (more work for little impact in my view) but did 2 x artificial swarms this year which will have knocked levels down...

    (All TBHs or warre.)

    Largely same with Association apiary's 13 hives.

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