# Does Oxalic Acid Vapor Kill Bees?



## ivashka (Nov 28, 2009)

Hi. I did Oxalic Acid Vapor twice about a month ago and it didn't hurt my bees. You should be fine as long and you do it correctly, 1 gramm of acid per hive body, 2 hive bodys - 2 gramms. And as far as I know you should do Acid vapor when there is no brood in the hive. I still did it when I had some brood but it didn't hurt them. Good luck.


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## camero7 (Sep 21, 2009)

Much easier on brood and queens than formic acid IMO. And very effective. However, if you have tracheal mites formic is necessary.


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## Michael Palmer (Dec 29, 2006)

Several years ago, I tried Oxalic vapor. Tried it over 3 seasons. Did the broodless November vaporization for two years. Still had high mite counts the following May. Vaporizer manufacturer said try 3 times in September, 1 week apart. Did an alcohol wash first, vaporized 3 times 1 week apart, waited 1 week and did another alcohol wash. Mite counts went up or stayed the same. 

I was concerned with possible damage to open brood, Marked areas of frames with eggs and larvae. At the end of the test, marked frames had all the brood sealed and/or emerging...which to me indicated that no damage was done to eggs or larvae. Not much was done to the mites either.


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## Adam Foster Collins (Nov 4, 2009)

Thanks for the replies.

Mike Palmer, Did you notice large numbers of dead mites right after you did the treatments? Or did you see much mite kill at all?

Thanks again,

Adam


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## Michael Bush (Aug 2, 2002)

I used the pipe version, but it killed a good 95% or so of the mites. There was no brood in the hive.


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## Michael Palmer (Dec 29, 2006)

Adam Foster Collins said:


> Did you notice large numbers of dead mites right after you did the treatments? Or did you see much mite kill at all?


I didn't look at mite drop. I use alcohol wash. Mite kill? I don't know, the numbers went up or stayed the same.


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## Adam Foster Collins (Nov 4, 2009)

The reason I asked the question of Mike Palmer is that I have found Oxalic vapor to be trickier to administer than I thought it would be.

I used the pipe method and found that if the pipe gets up against something, or gets jammed with bees, you don't get the results. I don't know what potential problems exist with proprietary vaporizers. I'm not saying Mike had any problem, but I do want to point out the possibility for the sake of others who might give it a try.

The first time I tried using Oxalic Vapor, I believe I had the pipe blocked with bees and/or wax, as afterward, there appeared no significant mite drop. I knew that I had a lot of mites, as I could see them on the bees, and had a lot of dwv. So I expected to see some notable drop after treatment. I was told by a friend to expect massive numbers of dead mites to appear at the entrance within the next 24 hours. I waited several days. None appeared. 

So I tried again.

This time, I made a new pipe and drilled a number of holes in the side of the pipe near the tip - hoping to make it less likely to be easily blocked. I was also very careful to 'feel' that the pipe had space around the end of it, by pushing it all the way into the vie, and then backing it off a bit to make sure it was free. This time, after the vapor treatment, there appeared massive numbers of dead mites at the entrances. I mean thousands of them. The looked almost like sand piled up on the landing board around the entrance.

So my sense is that it doesn't take much of a blockage to drastically reduce the effectiveness of a vapor treatment. 

Just something to keep in mind if you give it a go.


Adam


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## Mike Gillmore (Feb 25, 2006)

Application methods can be a bit tricky as you pointed out. Another point to consider, particularly with the pipe method, is maintaining a correct temperature of about (315 deg.F) while heating. If the temperature climbs too high (372 deg.F) the Oxalic Acid will not sublime but decompose to Formic Acid and Carbon Monoxide, reducing it's effectiveness. 

I've used both the Heilyser and Varrox vaporizers and they both work great. The sticky board will give you a good indication of how well it's working. A daily drop of 20-30 mites will change to hundreds or thousands in a 24 hour period following a treatment. I've never noticed any ill effects on eggs or larvae whatsoever when applied correctly, even after three consecutive treatments at one week intervals.


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## sjj (Jan 2, 2007)

Mike Gillmore said:


> ....A daily drop of 20-30 mites will change to hundreds or thousands ....



Another point to consider.

How many mites remain? 

- About 21% of the beginning mite population. 

It is a realistic estimate.


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## Jack B. Nimble (Nov 13, 2010)

If an oxalic treatment has an 80% efficacy, then three consecutive treaments will (at least mathematically) result in (100%-80%) cubed or .2*.2*.2 or .8% or a 1% survival rate.

Actually it wouldn't be as good because practically there will be a continual addition of new mites to the total population as bees emerge from the pupal stage. Also we are assuming that the lethality of the treatment is solely based on random probability when in fact a mite that has survived the first treatment may for some reason be able survive subsequent treatments.

But never-the-less, it does demonstrate how several treatments or combined methods can work but there is also a point of diminishing returns. For instance, to apply a fourth mite treatment would result in .16 % survival rate which is not much better than .8 %. At the same time, there is a detrimental effect each treatment has. There has to be. The big question is where do the risks and damage exceed the benefits?


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## camero7 (Sep 21, 2009)

But never-the-less said:


> Seems to me that doing an alcohol wash or something similar to test the results makes more sense. No need to treat if below the economic threshold IMO


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## D Coates (Jan 6, 2006)

Statistics aside I've not noticed any bee die off from oxalic acid vapor treatments. I've been doing it for four years now.


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## Jack B. Nimble (Nov 13, 2010)

Any treatment that you dispense to bees (or yourself) has risks and consequences. It is only done because there is a net benefit but still - there are consequences.

The concern where I live about multi-applications of oxalic acid in any form has a negative effect that will affect their winter survival. One of the concerns is what it does to their malpighion tubules and other damage at the cellular level that we wouldn't see as a beekeeper. A bee might not drop dead in a way that you would see it, but it may be suffering and its ability to thermo regulate in our extreme temperatures for a long time would then be impaired.

It is not as much a concern for beekeepers in milder climates because the demands on the bees are not as great. Also there is more brood rearing in southern climates so losses are compensated for. But here, there is five or six months of confinement will almost no brood rearing. So it is felt that multi-oxalic acid treatments would do them more harm than good.


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## Mike Gillmore (Feb 25, 2006)

Jack B. Nimble said:


> So it is felt that multi-oxalic acid treatments would do them more harm than good.


I'm not following you. Are you saying that the alternative, going through a long winter battling V-mites, would be better for the bees than multiple OA treatments?


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## Jack B. Nimble (Nov 13, 2010)

What I am saying is that multi applications of any mite treatment in the climate that I work with my bees needs to be considered with more caution that those in warmer climates.

Like the previous post of D. Coates, I have not noticed any bee die off after an oxalic treatment. But neither have I noticed any bee die off treating with other miticide methods either (except formic acid). However, there is an negative impact never-the-less regardless of what mite treatment you expose bees to which is why all treatments have a recommended dosage that should never be exceeded.

If bees are healthy, they can tolerate mites to a certain extent over the winter and multi applications of oxalic acid of any kind would do them no net benefit and probably damage them instead. In my climate, if they are not healthy and are have a high mite load, they are damaged by the mites regardless of any corrective treatment going into the winter and are as good as dead. Multi applications of oxalic acid may just change the nature of their demise with the mites giving them the coup de grace and the cold weather and exhausted food stores finishing them off in March. 

I have always been very cautious of not adding any more damage to my bees going into winter by hammering them toxic materials over and over. That being said, I do intend to try additional treatments of Oxalic acid vapour in the early fall on top of a last one in October. But in doing so, I have to consider the balance of the damage the treatments do versus their benefits. I have to also be conscious of the fact that for me, autumn is a bad time to knock back a heavy infestation.

At what mite infestation level can multiply applcations of oxalic acid be justified? I don't know. But I am sure it is somewhere between heavy and light. :scratch:


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## camero7 (Sep 21, 2009)

I now use the alcohol shaker method developed by Medhat. Over 10 mites/300 bees I treat. He recommends that you test bees again after about 2 weeks [something I haven't been doing but will next year] and retreat if still high. He has not reported any damage from the vapor treatment, although he seems to favor the oxalic drench.


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