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Discussion Starter · #1 ·
Finished treating my 40 hives last week and started to do mite counts this week just to be sure. After 3 treatments of oxalic acid vapour 7 days apart the first four hives picked at random had counts of 24, 11, 36 and 12 respectively. This is the first year that I am using oxalic acid vapour and wonder if it is really effective after all. Has anyone else had any problems with the system, I have started treating again with formic acid and fume boards
Johno
 

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Works really well for me and never had any problems. I highly recommend it.
 

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What was your mite counts before the treatments?
 

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What method did you arrive at your counts with? The usual way of determining the efficacy of a treatment is to test before and after applying the treatment.

If you had high mite infestation to begin with then Oxalic might not have been your best choice for treating as it requires multiple treatments to get at mites emerging from brood cells. The infestation rate of the hive would fall over time.
 

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I have improved results by going to 4 treatments 5 days apart.
 

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OAV works really well. If it is not killing mites, then there is a problem with your method of application.
 

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I have improved results by going to 4 treatments 5 days apart.
i was thinking about doing the same thing. How much of an improvement did you get?
 

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Now there's the question!!

I don't count mites so cannot give a definitive answer to that. What I can say is that where I am we have brood all year, no brood break at all to expose all the mites to an easy quick kill. So I started out using the standard 3 weekly treatments, but found it worked well with a lot of hives but some not good enough. So went 4 x's 5 days apart and have found a smaller number of hives needing remedial action later. But it's all rather subjective unfortunately, not really able to quantify it much better than that.

It's clear from reading the experiences of various folks on Beesource, that for some folks OA works really well and there could be many factors that influence that. For me, I have to work a little harder to get the needed results.
 

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I don't want to take over this thread, but I have one quick question, if I may to those doing multiple vapor treatments. Are you treating with the standard OA dose per frame of bees/deep each time you vaporize? And have you seen any adverse effects? (sorry that was two quick questions). My belief that multiple OA vapor treatments was Ok was recently called into question by another member when I suggested doing just that. This member stated that the directions that came with their vaporizer said one treatment during the brood less period, that "No one suggests multiple vapor treatments", and Implied that this was dangerous advice. I've been doubting myself ever since.
 

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Discussion Starter · #12 ·
Treatment consisted of two heaped scoops of OA per hive. Hives were one deep and two mediums or three mediums bottoms closed off and closed off after inserting the vapouriser , three minutes to vapourise then the heiliser removed the hive then closed for a total of ten minutes. The hole in my inner covers has I/8 screen stapled over it and I have lifted the outer cover to see if the vapour comes to the top and it does. I am starting to get the feeling that these mites are tougher than we think, after mite checking I took a mite and put it onto a microscope slide and put a drop of alcohol on it to stop it walking around the slide 10 minutes later I let some folks who came by to see how mite counts were done look at the mite. well he was once again walking around the slide so put another drop of alcohol on him, a half hour later the mite was gone from the slide.
Johno
 

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CB
For a number of years now I have been applying OAV one treatment per week for four weeks in August and have seen no ill affects to my hives. One applications per week for three weeks is the standard treatment with OAV, I give my hives a fourth application and have seen only healthy bees in my hives. The dose is 1 gram per deep box and is not per frame, OA dribble is applied per seem of bees.

I have found that people often confuse OAV with the OA dribble method, when using OA dribble one must use one application only in the Fall during broodless period, if more dribbles are done the bees life is severely shortened because the OA/syrup mixture is consumed by the bees and this severely effects the gut of the bee causing it to die earlier during the winter.

As far as the following quote below from the other member, I don't know of any vaporizers that would come with instruction like this. One treatment only per year could be done during the early winter broodless period but the damage from Varroa mites will have already been done by then. There are members here who do three vaporization's in September and then one additional application during the broodless periods between Thanksgiving and Christmas and this also works well but this timing is determined by your geographical location.

This member stated that the directions that came with their vaporizer said one treatment during the brood less period, that "No one suggests multiple vapor treatments", and Implied that this was dangerous advice. I've been doubting myself ever since.
A quick read through Randy Oliver's notes on Oxalic Acid treatment would be helpful to explain the different parts of this treatment which concerns you. http://scientificbeekeeping.com/varroa-management/treatments-for-varroa/
 

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Treatment consisted of two heaped scoops of OA per hive. Hives were one deep and two mediums or three mediums bottoms closed off and closed off after inserting the vapouriser , three minutes to vapourise then the heiliser removed the hive then closed for a total of ten minutes. The hole in my inner covers has I/8 screen stapled over it and I have lifted the outer cover to see if the vapour comes to the top and it does. I am starting to get the feeling that these mites are tougher than we think, after mite checking I took a mite and put it onto a microscope slide and put a drop of alcohol on it to stop it walking around the slide 10 minutes later I let some folks who came by to see how mite counts were done look at the mite. well he was once again walking around the slide so put another drop of alcohol on him, a half hour later the mite was gone from the slide.
Johno
And the next Science Ficition movie will be: "MacroMite, The Varroa That Couldn't be Killed"
 

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Thank you Bill! Yes, your description was exactly how I understood it. And in fact I had used both the dribble method and the vaporizer (using a home made pipe 3x at weekly intervals), and pointed out that he was confusing the two. That's when he gave me the following link to the instructions for his vaporizer: http://www.biovet.ch/en/Imkerei/varrox-vaporizer.html
When I read those I was kind of shocked, had never heard of using the vaporizing method during the winter cluster. Anyway, thank you for the information and I will from now on continue to use OA as you have described, appreciate it!
 

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i've no experience, and i assume that the three weeks apart treatments are aimed at getting to the mites that are in capped brood, but if your colonies have been brooding in earnest that may explain the mites that the oa didn't get.
 

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I've been using OAV at 7-10 day intervals, 4x. I've been pleased with the results. Oldtimer suggests 4x at 5 day intervals. Can someone familiar with the mite life cycle comment on most effective treatment interval?
 

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Discussion Starter · #18 ·
I do not think the mite life cycle matters, it is the bees brood cycle that counts. As the OAV only gets the phoretic mites, all the mites in the capped brood are safe, so the 7 day or 5 day cycle is aimed at getting the mites that have emerged as I believe the young mites have to be on bees for a certain period of time before going back to breed
Johno
 

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The phoretic stage of the mite lifecycle is 5-7 days, so it's possible with a 7 day OA treatment interval that a mite can emerge and make it back into another capped larvae before the next OA treatment. I have been looking for (but haven't found) good data on how many days after treatment the OA is still killing mites. I've seen drop rates, but these don't distinguish between mites that took a few days to die after being exposed as opposed to a mite that mite have emerged a day or more after the treatment and was exposed to lingering OA. Oxalic acid is very hygroscopic, so humidity in the hive will quickly convert the tiny crystals to a reactive solution, and my bet is the OA dissipates very quickly as it "bleaches the woodwork".

I have treated at 3-4 times at 5 day and at 7 day intervals, and anecdotally the 5 day treatment was more effective, but I need to do more controlled testing to be sure. With brood in the hive, OA is definitely not as effective as it is when the hive is broodless. My last round of several treatments at 7 day intervals in July only reduced the mite counts by approximately 50%. (Measured using the powdered sugar shake method, shaking for a solid minute to ensure reasonable accuracy of the count) I'm leaning towards either doing more frequent OA treatments during summer, or switching to MAQS for summer and OA for winter when the mite counts indicate it's time to treat (>2 mites per hundred bees sampled).

For what it's worth, I have seen nearly zero negative effects from using OA (Heilyser JB200). The bees perk up nicely when the mite counts drop.

-Knute

I've been using OAV at 7-10 day intervals, 4x. I've been pleased with the results. Oldtimer suggests 4x at 5 day intervals. Can someone familiar with the mite life cycle comment on most effective treatment interval?
 
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