# How Much Oxalic Acid is TOO MUCH Oxalic Acid



## BenjaminM (Mar 10, 2020)

When vaporizing, the recommendation is 1 gram of oxalic acid per brood chamber, on some schedule we'll say every 4 days for some number of treatments, we'll say 5.

If you really wanted to hammer them though, is there a point that you harm the hive or cause them to abscond?

10 grams per brood chamber every day for 30 days?

I am not asking about efficiency, I'm asking about the limits. Sort of a how many cups of coffee does it take to kill ya sort of question.


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## cwoodar0 (Jun 13, 2021)

So I vaped two hives every third day for the entire month of August and they were fine with it. I have vaped them once a month since.
Also, I put the maximum it would hold each time. About 3 grams each hive.


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## flibbidy_dibbidy (12 mo ago)

My bee mentor said he treated 18 days in a row to a hive just to see the effect. While they were pissed at him by the time it was done, he said they were no worse for wear. 
I've come across no literature that told of a lethal dose of OAV. Also recent studies are showing 1 gram is far to low a dose to be effective. Off the top of my head I want to say 3 grams is more effective in a study from U of Florida.


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## ShelleyStuart (Jan 4, 2010)

flibbidy_dibbidy said:


> My bee mentor said he treated 18 days in a row to a hive just to see the effect. While they were pissed at him by the time it was done, he said they were no worse for wear.
> I've come across no literature that told of a lethal dose of OAV. Also recent studies are showing 1 gram is far to low a dose to be effective. Off the top of my head I want to say 3 grams is more effective in a study from U of Florida.


The paper's behind a paywall, but the abstract gives the gist: Determining the dose of oxalic acid applied via vaporization needed for the control of the honey bee (Apis mellifera) pest Varroa destructor

Cameron Jack gave a talk for a WAS mini-conference about the study:


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## AstroZomBEE (Aug 1, 2006)

We use OA vaping on thousands of hives per year.
In our early testing we treated a single hive everyday for a month, 1 gram. No noticeable side effects after a month.

Aaron


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## G3farms (Jun 13, 2009)

AstroZomBEE said:


> No noticeable side effects after a month.
> 
> Aaron



Is that to you or the bees??

Just kidding!!


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## ffrtsaxk (Jul 17, 2017)

When you say "10 grams per brood chamber every day for 30 days?" do you mean 10 grams total per hive or do you mean if you have 2 deeps putting 20 grams into it? Yes, there is a point where it will start hurting the bees. An oxalic acid dribble is hard on the bees. If you put enough oxalic acid into your hive that you raise the oxalic acid content of their nectar/honey to the point of a dribble, it will also be hard on the bees. If memory serves me right, recent research has shown that treating with 2 grams per box is better than 1 gram, but treating with more than 2 grams per box does not improve results. I think they found that up to 4 grams per box was still safe for the bees when done about every 5 days.


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## BenjaminM (Mar 10, 2020)

ffrtsaxk said:


> When you say "10 grams per brood chamber every day for 30 days?" do you mean 10 grams total per hive or do you mean if you have 2 deeps putting 20 grams into it?


When I said 10 grams per brood chamber everyday for 30 days, I meant 10 grams "per" brood chamber (deep/box/etc.) everyday for 30 days. It is an arbitrarily high number. The point is to put a dot on the map and say "thats too much it'll kill your bees, or piss them off so bad they'll just up and leave".



ffrtsaxk said:


> If you put enough oxalic acid into your hive that you raise the oxalic acid content of their nectar/honey to the point of a dribble, it will also be hard on the bees.


How much is "enough"? What is "hard on the bees"?

According to Flibbiddy_Dibbidy, daily treatments of some amount for 18 days straight was fine.

Accoding to Cwoodar0, 3 grams every third day for an entire month (presumably 10 treatments) was fine.

According to AstroZombee, 1 gram every day for a month was fine.

According to ShelleyStuart, 0-4 grams once a week for 3 treatments was fine.

According to ffrtsaxk, 4 grams every 5 days was fine.


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## ursa_minor (Feb 13, 2020)

myrdale said:


> How much is "enough"? What is "hard on the bees"?


Look up Cameron Jack on youtube. His last interview with Kamon Reynolds stated that they do not know how much is too much yet, it had not been studied yet.


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## JustBees (Sep 7, 2021)

I observed that higher doses in my vaporizer resulted in un-vaporized acid delivered into the hive.

Test yours to see how much OA can be loaded without un-vaporized OA being delivered into the box.


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## BenjaminM (Mar 10, 2020)

JustBees said:


> I observed that higher doses in my vaporizer resulted in un-vaporized acid delivered into the hive.


This is interesting. I've noticed something similar. I am not convinced it is actually oxalic acid, but rather it is some other filler mixed in. At the set point temperature all oxalic acid will sublimate.

Usra_minor thank you for the link. I'll check it out this evening. From what I've seen they are both top notch guys.


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## JustBees (Sep 7, 2021)

I think it may boil in the pot and the resulting agitation may bring out some powder.

Maybe pot size and outlet location will affect this.


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## beebad (Mar 28, 2019)

I have to say, i have used OAV in the fall every 5 days until my mite load went to near zero. I have done this every year since 2018.’’ithink. All lade it thru winter.


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## AHudd (Mar 5, 2015)

BenjaminM said:


> When I said 10 grams per brood chamber everyday for 30 days, I meant 10 grams "per" brood chamber (deep/box/etc.) everyday for 30 days. It is an arbitrarily high number. The point is to put a dot on the map and say "thats too much it'll kill your bees, or piss them off so bad they'll just up and leave".
> 
> 
> How much is "enough"? What is "hard on the bees"?
> ...


Welcome to the conundrum that is beekeeping. There are few things that have high percent consensus. Each of the beekeepers you have quoted stated what works for them and likely would for others as well. They have arrived at their conclusions and methods based on factors particular to their situations. To further complicate matters, the bees differ on how well they handle mites.
I use two grams per brood box, up from one gram per brood box last season five days apart, sometimes six days. Okay, okay, sometimes seven.  I will continue to do so as long as it works.
I'm not even sure if less time between treatments would be cause to use smaller doses or if larger doses would mean we wouldn't need to treat as often. We each have to monitor our bees and be wary of those that speak in absolute terms.
Good luck with your bees, they are counting on you.

Alex


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## Marcin (Jun 15, 2011)

beebad said:


> I have to say, i have used OAV in the fall every 5 days until my mite load went to near zero. I have done this every year since 2018.’’ithink. All lade it thru winter.


How are you counting the mite load? By drops or alcohol wash?
And do you have a starting mite load count?


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## beebad (Mar 28, 2019)

Marcin said:


> How are you counting the mite load? By drops or alcohol wash?
> And do you have a starting mite load count?


I leave the ipm board in during the oav and then count every lousy dead mite carcass 48hours post treatment, which according to literature is the max effective reach of oav. I then put these into a spreadsheet and plot a graph. I treat until i see an anticipated drop in VD….otherwise no way to tell when to stop as i see people think they can do 1-2 treatments and call it a season. The starting mite count can be alarming, but expected since by the end of nov. it has been 3 months or so since summer treatment.


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## crofter (May 5, 2011)

My mite count system is pulling and examinining drone pupae when doing swarm assessment inspections. Late in Aug. I put a sticky sheet bottom under several of my colonies and if I have been seeing significant mites on drone brood I start OA Vapor on all hives and monitor mite fall on the sticky board hives. You could conceivably have considerable difference one hive to the next but not llikely if your bees are quite uniform in character; mine all get the same medicine. 2 gram OA every 4 or 5 days initially and if mite drop counts are rising as they commonly do in the fall, I treat every 3 days. 

I dont believe in allowing mite levels to increase to some arbitrarily considered action level. Mite levels must be kept near zero all during the time of rearing the wintering bees. Having the mite count arrive at zero some time *after* the wintering bees are raised is not good enough for high survival of bees in cold climate. Aiming for the lowest level of treatment for barely surviving is not my target.


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## GregB (Dec 26, 2017)

BenjaminM said:


> When vaporizing, the recommendation is 1 gram of oxalic acid per brood chamber, on some schedule *we'll say every 4 days for some number of treatments, we'll say 5.*


If done on a brood-less colony - a single treatment is sufficient for a large timeframe.
Thus you should not be thinking "how much is too much".
Instead, you should be thinking - "how I make it so that a single-treatment is sufficient"?


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