# first treatment with OA



## Ben Little (Apr 9, 2012)

Hi i did my first treatment with vaporized Oxalic acid 2 days ago and had a sticky board on and today i checked the boards and only found about 10-11 mites on each board total. Is this unusual for strong hives? they were nucs i bought in early may. should there be more mites falling off? or do i just have a low mite count because the bees are building resistance or something. i have never treated them with anything all year and they are my first i ever owned.


Ben


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## BigGun (Oct 27, 2011)

The fall should start going up. Supposed to start slow from what I understand.


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## Mike Gillmore (Feb 25, 2006)

What kind of 24 hour mite drop did you have before treatment? If your board was clear after a 24 hour check prior to treating you may just have a colony with a very low load of mites. 

Did you use an electric commercial vaporizer or a homemade pipe unit? Some of the pipe type vaporizers that are heated with a propane torch can be tricky to use. The temperature when heating up the acid crystals needs to be in a specific range for the vapor to be effective.


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## Ben Little (Apr 9, 2012)

I used the Heilyser Vaporizer and followed the directions with the proper Oxalic acid from Bee Maid. I think it must be a low mite count.

Ben


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## Mike Gillmore (Feb 25, 2006)

Sounds like you are in great shape then. Those are very low mite counts following vaporization.


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## Sasha (Feb 22, 2005)

Mites are hidden in the brood. You need to treat multiple times to reach most of them. Like three or four times, 6 to 7 days apart.


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## Daniel Y (Sep 12, 2011)

I have been pondering this issue of application of OA in order to insure that all cells are treated while uncapped. This requires a careful look at both the capped cycle of drone and worker brood cells.

Drone cells are capped for 14 days. worker cells are capped for 13 days.

1 second before you apply OA a drone cell is capped and the treatment is in effective. In addition one second after the treatment is in effective a drone begins to emerge that the treatment also missed. I am saying the treatment was effective for 10 minutes.

Assuming that the queen lays a new egg immediately that freshly opened cell will be capped again in 11 days for a drone, 8 days for a worker cell. To insure that all cells that have been opened since the last application you must retreat in 7 days or less. Still half the cells that where capped at first treatment are still capped at second treatment. to unsure those cells are treated while open at third treatment you must treat at 14 to 15 days from the first application.

THis might help it make more since.

Drone brood has 14 days in which it is capped. Numbers cells 1 through 14. Worker cells are capped for 13 days numbers cells 1 thru 13 application one treats all open cells and no capped cells for either worker cells or drone cells.

During day 7 all drone cells 8 thru 14 have emerged and are still open cells. also all worker cells 8 thru 13 have emerged and are still open.

Note the cell that had a bee emerge one second after first application was no longer effective will be recapped on day 9. waiting ten days to treat will result in this cell being capped for all three applications. You only have 24 hours to treat this cell when uncapped.

During day 14 from fist treatment all remaining cells that where originally capped will be open. IN this case you have a window of as much as 72 hours before they will be capped again.

I have seen it recommended that you treat with AO three times spaced 10 days apart. to as frequently as three to four times 7 days apart. as the above close look indicates. 10 days apart will fail to treat all cells. 7 days is a tight fit for the first two applications with a bit more wiggle room for the third application. 10 days does not work for any of the three applications. cells will be missed at every treatment.

Due to this I suggest 3 treatments spaced strictly, 7 days apart.


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## crofter (May 5, 2011)

Daniel, I agree with your math. I believe the deposit of oxalic crystals throughout hive surfaces does have a lingering effect beyond the 10 minutes or so vaporizing process but I would still not want to allow more than seven days between treatments. The beauty of the method is you dont have to let weather interfere and I suppose you could even treat at night since you dont have to open the hive.


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## jim lyon (Feb 19, 2006)

The problem with using OA to try to control varroa in a hive with an actively laying queen is that the vast majority of varroa in the hive (I have heard estimates of up to 85%) are contained in sealed brood. Daniels suggestion of treating every 7 days is certainly better than a treatment every 10 days from a mite killing standpoint but it really only marginally helps the overall picture. His statement that an application lasts for 10 minutes, though a bit exaggerated, is a pretty good synopsis for how OA works and why it is virtually impossible to get any type of varroa control with brood present in the hive. Oxalic has virtually no residual effect and bees are constantly emerging with varroa that will almost immediately move into larvae that is within 24 to 48 hours of being capped. I have experimented with using OA throughout a summer to see if control can be achieved but could never really see much progress being made in reducing overall mite counts. My conclusion is to stick with the accepted and very effective practice of a single application well timed late in the fall when there is little or no sealed brood in the hive but before temps drop too low. If a treatment is needed earlier then I would recommend thymol, Hopguard or MAQS.


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## Daniel Y (Sep 12, 2011)

I am certain my 10 minutes is conservative to the extreme. But just so people don't have to guess. to whatever degree the treatment is effective is only making that window from treatment one to treatment two longer. Suppose the OA is effective for 24 hours. you now have two days wiggle room for treatment 2. using a ten minute effective time range is a worst of worst case and the timing at 7 days still works with 24 hours to spare.

I also don't think the queen is setting at the edge of the cell waiting to lay an egg in it. Again worst of worst case with any delay only opening the window the cell will be uncapped. It is very likely that in reality you have a couple of days wiggle room for the second treatment. But a 7 day interval guarantees that no cell can possibly be capped for all three treatments. Not even if a pupa is 24 hours late in emerging.


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## camero7 (Sep 21, 2009)

jim lyon said:


> If a treatment is needed earlier then I would recommend thymol, Hopguard or MAQS.


I don't see much difference between hopguard and OA vapor. Both require 3-4 treatments. I have achieved decent control of mites with OA vapor. Just did a alcohol shake after 4 treatments and am averaging less than one mite/hive. I will treat around Thanksgiving to clean up the residual mites. I like OA for ease of application and cost [pennies/hive].


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## jim lyon (Feb 19, 2006)

camero7 said:


> I don't see much difference between hopguard and OA vapor. Both require 3-4 treatments. I have achieved decent control of mites with OA vapor. Just did a alcohol shake after 4 treatments and am averaging less than one mite/hive. I will treat around Thanksgiving to clean up the residual mites. I like OA for ease of application and cost [pennies/hive].


Glad to hear it Cam. Perhaps I am not comparing apples to apples here as we have used trickle applications and not vapor. I do think, however,that there is a difference in the compounds in that Hopguard is designed for an extended treatment, not so with OA. Are you theorizing that there may be some residual control where an oxalic treated larvae too young for varroa to move into may still kill a mite that moves into it in the critical timeframe shortly before capping? I am trying to justify in my mind how a mite that may only see the light of day for as little as 24 hours can be controlled with treatments of a non residual compound a week or more apart. Help me out if you feel there is another dynamic in play that I am not factoring in


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## camero7 (Sep 21, 2009)

Jim, I really don't have any studies to back up my observations. I do know that OA condenses in small particles in the hive and I believe the bees cleaning them out helps. All I know is that, so far, my method has worked pretty well. Had 100% survival of treated hives last winter [but then it wasn't a real winter]. This winter should give me a better idea. I do know that my spring counts were very low and I didn't think I needed to treat. Since bees were raising more brood last winter than normal, I felt it was a good test. Should add that I only use VSH type queens in my hives and that is probably another factor in the low mite count. Also I have decided to treat in the early fall every year, no matter the count, to try and hold down the virus issues the mites bring. I think this may have helped with my survival rate.


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## Daniel Y (Sep 12, 2011)

Jim, very good point on the issue of what happens to the cell that was capped 6 days after the first application and had a mite that came out of a cell that was capped at the first application.

First of all this is why no treatment is good enough to get all mites. Not unless you had a treatment that is effective for 14 consecutive days and will kill all mites as they emerge from caped cells. 

an in depth evaluation of this situation is far more complicated. But I am breaking it down. I hope to come up with some sort of calculated percentage of possible surviving mites but at best there will be significant guess work involved. 

I also need to know more about the life cycle of the mite. Is there any time period for the mite between it being freed from the capped cell until it will enter another cell? For now I am saying a mite can leave a capped cell and immediately enter a cell being capped.

I am also assuming a 100% kill rate of any exposed mites. I know this is not true but the issue needs to be cleaned up in order to crunch numbers.

So after the first treatment only cells that are still capped will have living mites in them. 

Allowing for there to be no free roaming mites, and that egg laying is consistent throughout the 14 day period. 58% of all mites will not be exposed to the first treatment. I came to this number by the following method.

Drone brood is 24 days in development from egg to emergence. of those 24 days it is capped for 14. 14/24 is 58%. This means it is possible that only 42% of the mites in a colony are exposed to the treatment.

Worst case scenario is that this is the best we will ever get. Since it is arguable that any mite from a capped cell can and will simply move to another capped cell. Or to a cell that will be capped before the next treatment. 

This is where it gets complicated and more details information is critical. Two factors can drastically influence that actual kill rate.
1. how long is Ao effective after treatment?
2. How long does a mite remain exposed in the hive after emergence?

I will just put in some numbers for both simply to show how much they effect the final numbers.
1. I will say 24 hours. this alone reduces the percentage of mites that avoid exposure to 54%

2. would be a reasonable time the mite spends roaming the hive. hitching rides on bees and mating. I am goign to give it three days. This alone reduces the number of mites avoiding exposure to 45%.

I am not at all certain that 100% of all mites that where in capped cells will find themselves in capped sells at the time of the second treatment. I consider it more reasonable to assume that a comparable number to those that where in capped cells in the first place. or 58%.

This breaks down to real numbers as.

We start with 100 mites. after the first treatment 58 remain. after treatment two 33 remain. and after treatment three 20 remain. These numbers reduce further if there is any delay in a mite going from capped cell to another capped cell. if it takes three days for a mite to do so the numbers are.

54 mites after treatment 1 24 after treatment 2 and 10 after treatment 3.

This does show to some degree how much even small details can effect the actual kill rate of AO treatment.

IF there is some significant period of time that a mite remains exposed before entering another capped cell. this could be very important. It could also completely alter the recommended treatment schedule. Again assuming the mite will remain exposed for three days. then a treatment schedule of 5 treatments spaced every 72 hours would expose every mite in the hive.

5 treatments 3 days apart spans the entire time that drone brood is capped. 72 hour intervals catches every mite during it's mating period. once you have the vaporizer, AO treatment is dirt cheap and I have heard over and over it is nearly impossible to overdose bees on it.

This may very well be another avenue worth exploring.


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## crofter (May 5, 2011)

I was going on the assumption that the mite was phoretic for an average of around 4 days before getting back in a cell and that the OA presence damaged their feet and probiscus. I think I read that but it needs fact checking for sure. I have not used it yet and wont till November but I was hoping that it could be used next summer with similar effect to hopguard. I had good results with it but can certainly see where it could have a longer affective period than Oxalic vapor.


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## jim lyon (Feb 19, 2006)

Daniel: I am not sure that I am fully digesting all of your math but I think you are headed in the right direction in that it may take treatments more often than 7 days. One other thing that is dawning on me as I read this is that there may well be a distinct advantage in using vapor over trickle and that is that the mites that have infected the open larvae and are "snorkeling" until the cell is capped may well be killed by vapors but not by the direct of trickling. If that is in fact the case that additional 24 to 48 hours of treatment may be a considerable advantage.


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## camero7 (Sep 21, 2009)

Not all mites enter the brood. Many remain on the brood bees. I believe that the absence of drone brood [this time of year] also decreases the amount of mites in the brood. All beekeepers should read the Rosenkranz paper concerning varroa [best paper I've seen yet on it] excerpt below. 

_You also need to allow for the fact that not all mites enter the brood, many remain on the brood bees. also not all females that enter the brood reproduce:It is important to consider that not all fertile Varroa females, i.e.females which lay at least one egg, are really reproducing successfully.The production of one adult viable daughter requires at least the maturation of one male and one female offspring including mating. Therefore, female mites producing only one egg, no males or with delayed start of oviposition may not contribute to the growth of the Varroa population_[/I]


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