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Discussion Starter #1
Hi,

I'm not getting good results with vaporized oxalic acid and would like your thoughts. I've done 4 OAV treatments and my way too high (20 to 24 per 300 bees) mite number aren't really coming down (I'm only counting one hive but I am treating all six). All hives have screened bottom boards (well sealed during the treatment), slatted racks, and two deeps, except one that only has one deep (not the one being counted). Two overwintered and four were splits from those two this spring/summer.

I have a standard cheap 12V vaporizer and 98.5% oxalic acid from Amazon. For the first three treatments I was using a lawn tractor battery and it was too weak for my six hives. It took 4 to 5 minutes to vaporize in a test burn and after the first hive or two would leave a brown/black residue. There would be some dead mites on the screened bottom board covers, after 24 hours, but not hundreds. However, after 3 treatments over two weeks, the mite count hadn't changed (see below for details).

I figured that the battery was the problem so got a 300W 12V plug in power supply. Test burns looked much better, 3 to 4 minutes, and no residue was seen after either test burns or actual hive treatments. I was therefore very disappointed that 3 days after my first treatment using the power supply the mite count still hadn't dropped appreciably.

Details are below:

7/27: Mite counts 24/300 (first time I counted this summer; the summer got away from me a bit)
7/28: First OAV (battery)
8/3: Second OAV (battery)
8/8: Third OAV (battery)
8/10: Mite counts 24/300
8/16: First OAV with power supply
8/19: Mite counts 20/300

I've ordered Formic Pro and will put that on as soon as it arrives and will stop the OAV treatments for now, but I would still like to understand what is going on with my OAV failures.

Observations:

1) The oxalic acid I have turns brownish/dark in my test burns, which is different from what I have seen in online videos.
2) The oxalic acid I have is flakier/stickier than the powder I see in online videos.
3) I seal up the hives pretty well, but am able to see small wisps coming out of various places on the hives, so it seems that the vapor is moving about.
4) Now that I am using the power supply, the chamber is empty when done, although the chamber is now darkened to a sort of chocolate milk color.

Any thoughts? Is my oxalic acid bad? Am I incorrect in thinking that the counts should have dropped substantially 3 days after what seemed like a quality treatment with a good power supply?

Thanks for any suggestions you might have.

Brian
 

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You will not likely get a good mites count 3 days after a single mite treatment with OAV as you can only kill phoretic mites and 80% of your mites are still in the brood and are emerging day by day. However with the counts you have shown you should have had a large mite drop after a successful OAV treatment. I would try to find some other OA, try Amazon and get something from Florida Labs. In my opinion you will need at least 5 treatments and then maybe 5 more to get that mite count down.
 

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You should be able to purchase OA from a local hardware store. Many beekeepers use the Savogran Wood Bleach OA. Like this.

https://www.contractorswholesalesup...XT32uQPN7jTAIJoJGYVGZpTgTNRjU25xoCsD4QAvD_BwE


What were your mite counts on the tray 3 days after the treatments? With the shake results you are getting I would expect you to find hundreds, maybe thousands of mites on the tray. Sounds like you may have a bad batch of OA, or there may be a problem with your vaporizer or power source. Formic Pro will take care of your immediate mite problem while you figure this out.
 

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I would agree with the 2 previous replies that it is time to change the OA you are using. I have always used Savogran brand (also bought from Amazon) without any issues. The fact that it is leaving a residue is extremely alarming.
 

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The OA lable reads "Use only in late fall or early spring when little or no brood is present. Oxalic Acid Dihydrate might damage bee brood. Oxalic Acid Dihydrate will not control Varroa mites in capped brood. "

while the internet tells ya other wise, its a poor and illegal choice for summer treatment, yes it can "work" if you do it enuff times
Johno says it well
In my opinion you will need at least 5 treatments and then maybe 5 more to get that mite count down.
yes it can "work" if you do it enuff times

As a side note, the Savogran Wood Bleach comes in at 99.7%. Your 98.5% may be why your seeing residue
 

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I have a standard cheap 12V vaporizer
I haven't seen any sort of 'cheap' vaporizers. Maybe we have different definitions of cheap.
What brand?
 

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I think you are wise to get some formic on them asap. I second what others have suggested: Maybe bad OA, but the real reason it seems you are not making progress yet is 80% of the mites are under the cappings. As the bees hatch, more are released just as your population is declining. J
 

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Discussion Starter #12
Thanks for all the advice.

I went ahead with the Formic Pro, and it caused a mite drop in the high hundreds to low thousands, so that is encouraging. I understand the issues with OAV and brood, but the upper temperature limit with Formic Pro can mean weeks at a time that it can't be used here. Luckily we just had a cool spell so I could get it on right away.

I hadn't noted above, but the mite drop after OAV using the power supply was in the mid hundreds, which was definitely more than when I used the battery. When I do want to use OAV going forward, I will use the power supply, get some Savogran OA, and see whether that helps.

Regarding the vaporizer, I am using the Varomorus Durable OXALIC Acid 12V Vaporizer, which was $60. Perhaps not cheap, but compared to some of the other options, a bit more affordable (assuming it is effective).

Thanks again.
 
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