How to do Oxalic Acid treatment?

[David LaFerney]

I did OA treatments on my 2 hives about a week ago, but I'm still seeing a lot of mites on the sticky boards (100/24 hrs more or less)  maybe I did something wrong:

First thing in the morning of good weather I blocked the entrance to keep the foragers from coming out.

About 10 oclock I came back to do the treatments - when they would have normally been flying out.

Both hives are 8 frame mediums - one has 3 boxes full of bees + an empty box to feed in - the other has one box of bees and an empty to feed in.

I dosed the bigger hive with 2 grams and the smaller hive with 1 gram - carefully weighed on a reloading scale.  I'm thinking these dosages might have been too small - I got them from the online instructions of a commercially produced vaporizer.

The hives are already tight with only one bottom entrance and everything propolised so I didn't seal anything with tape - but I didn't see any vapour escaping except a very small amt around the vaporiser pipe.

My vaporiser is made out of 1/2" threaded iron plumbing parts - I put the OA crystals into a threaded cap and heated it with a plumbing torch for a couple of minutes.  When I was finished there was a very small amount of powdery white residue left.

I inserted the vapor pipe through a tight hole in the back of the IPM oil trap bottom board below the screened bottom.  These bases are completely enclosed - not open SBBs.

I left them closed up for about 15 minutes before letting them out.  They seemed no worse for wear and tear.

It seemed like there was a large drop right away, but now a week later I'm still seeing a lot of varroa on the sticky board.

I would especially appreciate some insight from people who actually use OA vapor treatments.

Thanks 

[Finski]

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When you treat with oxalic acid, mites will die during next 4 weeks. The peak is about after one week.

[David LaFerney]

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When you treat with oxalic acid, mites will die during next 4 weeks. The peak is about after one week.

Thank you.  That is extremely helpful.  So, I did it about right?

[Hethen57]

David....I am observing the same thing, a major drop, then a continued drop, after my first two rounds of OA treatment.  Also, I have not had any powdery residue in my copper pipe setup after 60-90 seconds of low propane heat.  First you can hear it bubble in the pipe, then you keep heating and it vaporizes.  There is some minor residue around the hole where I insert it into the hive.  You may want to try copper sometime because it heats so quickly and easily.  You can pretty much gauge its temp by appearance after you have done it a few times.
-Mike

[D Coates]

I did a couple this weekend.  I use the Heilysler unit.  From what you're describing you did it right.  I listen to the side of the hive (upwind) and you'll hear them start fanning their wings with a dull roar if it's working correctly.  I do it 3 weeks in a row in November.  You didn't mention what temperature it was.  I like to do it when it's around 50 degrees as 99+% of the hive is in there but they aren't too tightly clustered.  I do have a small breather under the outer cover all year round that I normally see light wisps of "smoke" come out of that let me know the vapor has made it all the way to the top.

I don't count mite falls though.  I figure if the hive was so infested it needed additional treatments I don't really want that queen next year.  I also overwinter some nucs with fresh Fall queens when spring comes to fill the ranks of any hives that have failed.  Knock on wood it's only happened once in my short four years.  I also do IPM with drone frame removal, SBB's and some powdered sugar dusting.

[Michael Bush]

I observed a continued drop for about a week after treatment, and then I did another treatment...

[bernanos]

Michael, I'm confused.  I thought you didn't do any treatment.  Are you now recommending Oxalic acid?

[David LaFerney]

I did a follow up treatment 2 weeks after the first one,  and I am now seeing just a few mites drop.  I wish that I had done the treatments in August before the fall brood was being raised, but live and learn.