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Discussion Starter #1 (Edited)
I know in the U.S. oxalic acid is approved only for treating a broodless hive, so this is just a theoretical question:

For OAV'ing a hive with brood, the rule of thumb I have heard is 3 treatments 7 days apart, or 4 treatments 5 days apart. The idea being, that since OAV doesn't kill mites in the sealed cells, you have to repeat treatments to get the mites as they emerge from cells that were sealed before OAV'ing started.

The general idea makes sense, but I don't understand the reasoning behind the timing . . . ?

Workers are in sealed cells for 11 days, and drones are in sealed cells for 14 days. I am sure I am just being dumb, but wouldn't this mean that any series of OAV treatments to get all the emerging mites would need only span 14 days? In other words, OAV'ing over a period of 20 days or 21 days is longer than needed, and is actually counter-productive because it has the effect of "diluting" the treatment.

Add in the fact that OAV seems to lose effectivity after 3 days, and it seems to me that if one were planning on doing a total of 4 OAV treatments, wouldn't it be better to spread those 4 treatments over the 14 day period for all capped brood to emerge rather than the aforementioned 20 days? Put another way, 4 treatments spaced 4 days apart would provide almost continuous effectivity for the time period for any and all capped brood to emerge, which would kill more mites than a treatment schedule having gaps of effectivity?

Just wondering out loud . . . .



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Treating 3 times, 7 day apart gives you a total of 15 days. Treat on day 1, day 8 and day 15. Treating 4 times, 5 days apart gives you a total of 16 days. Treat on day 1, day 6, day 11, day 16. Both cover the period that the brood is sealed.
 

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With the unknown length of effectiveness between treatments, I suggest that 7 days apart may not be as effective as a sequence with one extra application resulting in smaller gaps between doses. If a colony truly is completely truly broodless it probably does not matter. How likely is that?
 

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Right now i'm trying the glycerine/OA blue shop towel application method on a few colonies with high mite levels. The idea is the bees remove the shop towel over the course of about a month so the treatment is spread out across a few mite cycles. First time using the method so I can't attest to efficacy, but there is a good write up on Randy Oliver's website on the method and Randy seemed to have success with it. Good luck.
 

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Discussion Starter #5
With the unknown length of effectiveness between treatments, I suggest that 7 days apart may not be as effective as a sequence with one extra application resulting in smaller gaps between doses.
This is kind'a what I am getting at. I pretty much never see any dead mites after the 3rd day after an OAV treatment. Consequently, waiting another 4 days (i.e. 7 days, total) to do another OAV allows 4 days for mites to emerge from cells, and then go back into another cell to be protected from the next OAV treatment. Why give the little bastards that opportunity?

For the reasons stated above, I, too, am thinking 3 evenly-spaced treatments is inadequate. And, if you are going to do 4 treatments, why not space them 4 days apart? Treat on day 0, treat on day 4, treat on day 8, treat on day 12. The 4th treatment on day 12 will kill mites through day 15. This treatment schedule covers 14 days, with a substantially reduced period of in-effectivty between treatments.

Of course, treating the hive when broodless is by far the best procedure when using OA.
 

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After emerging from a cell mites are phoretic for about 5-11 days. Therefore, if the treatment stops being effective after 3 days any mites emerging over the next 4 days will still get hammered when treating on day 7 ... during their phoretic period.

Saying that ... I treat at 5 day intervals.
 

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I have seen it stated that repeat breeders can jump back in a cell immediately and that 4 days is close to the mean phoretic period. I haven't seen a write up of a controlled experiment to weigh the difference in effectiveness of 7 days vs a shorter period but that is the way I lean.

We don't know what all politics and advertising rationale was applied to create the advisory 7 day period; Perhaps if a results oriented beekeeper was at the helm, the label might read a bit different!
 

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Remember that under all methods of treating, the best you can do is knock them down to manageable levels. The most important treatment is the winter broodless one. In my area, that one keeps the hive healthy from mid-December through early August. I also prefer the every 5 day treatments because I feel (no proof offered) it does a better job that way.
 

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Right now i'm trying the glycerine/OA blue shop towel application method on a few colonies with high mite levels. The idea is the bees remove the shop towel over the course of about a month so the treatment is spread out across a few mite cycles. First time using the method so I can't attest to efficacy, but there is a good write up on Randy Oliver's website on the method and Randy seemed to have success with it. Good luck.
Please keep us posted with your results. Anyone else trying this method, ditto.
I understand this method is not yet approved by FDA, but I am very curious.
 

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Discussion Starter #11
I have seen it stated that repeat breeders can jump back in a cell immediately and that 4 days is close to the mean phoretic period.
I know this and similar numbers get put forth for the phoretic period of mites. I see similar time periods cited in papers, but with no supporting evidence or study cited. What is the average and, just as important, what is the standard deviation of the phoretic period? Can anyone post the actual source of such information?
 

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With brood present, treat 7 times 3 days apart. Or you wreck your bees in years with high mite loads. This is the experience from overseas with +30 years of using oav. Feel free to do your own experiences (and re-invent the wheel...).
 

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Discussion Starter #13
Bernhard - Thanks for the info! This is the first time I have seen the 7x, at 3d interval schedule for a brooding hive. It makes sense to me! I know the Europeans are way ahead of the Americans when it comes to using OAV. How well accepted is 7x @ 3d schedule in Europe?
 

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Not very well. The bee researchers don't do much studies about oav for some reasons (political reasons). All hand down experience by some sturdy oav-users. Those who follow the official recommendations usually get into trouble in certain years and - of course - blame oav for it. While the others have ecxellent results. Year after year.

Only too much work. That is the major disadvantage.
 
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