Oxalic Acid

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Red Bee

House Bee
Dec 11, 2008
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Hive Type
Hello all. I'm after some advice please. I'm planning on using Oxalic acid this winter to treat against varroa. It will be my first attempt so i was just wondering what the reaction might be from the bees? Will they growl, will they get teasy or will they do nothing? Also when would be the best time to treat, December is when i've read is best but also that depends on the temp being right? I've read on this forum some people leaving it until January when the weather has really dropped. Any tips would be greatly recieved.:)
I'm no good at forecasting the weather (probably as about as good as the met off. for further ahead than ten days), so no good asking (me) for when to do it. Do you have a known varroa problem which will need attention?

I would be monitoring for mite drop and only treat if appropriate. There are always risks involved with with oxalic acid treatment and particularly any disturbance at that time of the year.

OK, varroa may be the greater of the evils, so go ahead if that is the case. Bees will probably hardly notice you as it should actually only mean having the hive open for a minute or so. Might depend a bit on where they are on the comb.

Presumably you are trickling, not evaporating?

Regards, RAB
just on weather, we had first snow this morning, covering above 250m locally.

I track this link below for my medium weather plans, it can behave like a snake at times but the more agreed the top temp lines the more accurate it tends to be, as of today you can see agreement in the models until around the 3rd Dec
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While I too am a new beekeeper and so far have not used Oxalic Acid, here are some things I have found out to date.

Firstly, I shall state the obvious. It is poisonous and so should be handled with care and kept out of reach from pets and children, etc. Take a look at Dave Cushman's site for the treatment by Wally Shaw. It has some useful tips on handling the substance!

However, this is not exactly the receipt I shall be using, I am using a lower amount of Oxalic acid, recommended to me by good authority, who has used this method before. The receipt I have is:

"The recommended mix is 45g of Oxalic Acid in one litre of sugar syrup (1kg sugar to 1 litre of water mix ratio). This is then trickled on the bees at 5ml in each occupied bee-way between brood combs. Timing of treatment is when there is virtually no brood in the hive, depending on the weather this is late November/December."

If you need more information A full research article can be found at ...

Hope this helps.
I was going to add before I accidentally hit "post reply", that you should read Dave Cushman's Warning at the bottom of the page, concerning Beekeeper Protection, it reads, quote:

It cannot be stressed too strongly that oxalic acid is an aggressive substance and needs to be treated with respect. Acid resistant gloves and goggles should be worn and an apron of the type used by mortuary attendants, along with wellington boots that have the tops covered by gaiters so that any falling liquid cannot fall into the boot. A respirator that has specialised organic acid filtering will be required in cases where the acid is sprayed or vapourised. Oxalic acid is also poisonous to humans by ingestion.

Not so sure I want to use the substance after reading this!
Yes, oxalic acid used to be kept in the poisons cupboard.

That apart, it is just common sense precautions similar to those that children have to take when taking lessons in a school laboratory.

No eating, drinking (or smoking - for adults), wear appropriate personal protective clothing, etc. to avoid any contact, and take care not to endanger people (nor flora or fauna).

There are many such substances/items out there. You just treat them with caution and respect. Farmers use pesticides, some of which are/were very harmful. Shooters use guns! Drivers use vehicles.

There will always be the small percentage of 'accidents' - most are not accidents because they were not an 'unavoidable occurrence'. Proper risk assessment will quickly identify areas needing special clothing/attention.

If you are not entirely confident of your ability to satisfy the above conditions, then, yes, avoid any risks by not using it. So FenBee, you should be looking to find an alternative for oxalic acid treatment in your 'varroah armament'?

Alternatives might be to employ someone to do it, go to classes or take a course with a competent person/beekeeer or adopt a slightly different IPM system.

Regards, RAB
I have some pics here from last year:
As you can see I waited until we had a nice hard ground frost before treating,I put on an extra pair of trousers,an old bee top and a pair of leather gloves with a pair of marigolds on top.

Each hive took under 2 minutes from lifting the roof to putting it back on.

The bees never even new I had opened them.
I have used an oxalic trickle method for the last 2 years. I make up my own solution, the bees accept the syrup solution without any anger or distress and the results were that I knocked off loads of varroa (500/700 when the drop the day before was 5). I have not had bee loss after these treatments

Insert inspection board under open mesh floor

Get very sensitive scales to measure the Oxalic powder.
Make up a 1 pint to 1 lb of sugar to make syrup.
Wear a mask over mouth and rubber gloves. Protect eyes unless stirring VERY slowly and carefully.
Add 20 grammes of O.A. powder to half a pint of the syrup. Stir till dissolved in the warm syrup.
Draw up 55 mls of syrup/Oxalic mix into a syringe.
Open hive
Trickle 5 mls of the solution over each seam of bees. Trickle same over each untill all seams are covered with a little syrup.
Close up hive.

If treating a few hives ensure the liquid doesn't cool too much. The bees will appreciate the gentle warmth, not a cold syrup.

I will wait until we have had 2 weeks of cold to ensure brood minimum, but a warmish day to open the hive - bit of a juggling act
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Oh boy fenbee! You have strange friends.
Lowered acid amount too low dead rate to mites.

oxalic trickling has been researched carefully 10 years and you are again Making your own recipes

the right one is for 3-5 hives:
take a digital kitchen balance
100 g sugar +100g water +7 g o acid
you too heather!
Why you deliver your recipe?

And mask! Oh boy! It does not evaporate.
I would be monitoring for mite drop and only treat if appropriate.

This is very bad advice.........given that a mite drop counted on a tray is only an indication of how many have dropped in the last half hour or so and is very little indication of the load the bees are actually carrying. If you see any mite at all you should be treating. Actually if you treated during the autumn you should be treating again in winter, and if you live in the British Isles you should be treating (unless you're HP of course:))

Since Oxalic acid can be purchased ready mixed and all you have to do is syringe it onto the seams of bees I don't see quite why it is such a major scare story. Wear rubber gloves and a mask if you want, but do watch how you cross the road to get to the bees..............:hat:

This is a good link for making your own up.


But simpley you are looking for a 3.2% solution,

small scale

7.5g OA in a 1:1 sugar water solution (100g to 100ml) will do for approx 4 hives

A box of OX is about £7 for 500g, and as a powder OA will last for years, it is just when you make it up into the 1:1 solution it is best to use it within a few days.

or just buy it ready mixed e.g About £3 for 2 hives

Agree Frisbee - buying ready made up solution is fine- but I made own up and the first time with no mask - I did have sore throat for a few hours.

And Finman - what's wrong with writing a recipe. It is tried and tested- it killed varroa and didnt kill bees so must be fairly safe to print.
as a first year bee observer! (still dont feel i can claim to be a beek bees are just being nice to me at mo!!) I will be using what if feel is the safest method - PHONE A FRIEND!!! Course leader I went to last year has said she is more than happy to help when needed - as of yet I havent called on her services, but think I will for this one!
Thanks for all of your replies. I have bought the ready made oxalic acid to start with. I have also treated with Apiguard in Aug/sept. Last season i had 2 hives out of 5 with visiable varroa & deformed wings, called the local expert in & had to treat in the summer. I want to do all i can to reduce varroa numbers for next season so i don't see things like that happening again!
Bad advice eh? I wonder why you should be treating hives with no appreciable varroa loading? They are out there, you know.

If there is little infestation left when you do your thymol treatment, and sometimes little before that, why subject the bees to an unecessary 'medication' or 'hive cleanser' only a few beeding cycles later. I think I only have a couple of colonies which are likely to receive an oxalic acid treatment. The rest will have far less than the accepted harmful mite threshold. Your bland comment of 'if you see any mite at all you should be treating' is, frankly, rubbish. Perhaps you were one of the beekeepers who hastened the resistance to the miticide strips, like apistan, by treating for far too long and treating mites with a sub-lethal dosage.

Whatever treatment you give for varroah control, there will be survivors or reinfestation. FACT OF LIFE. Newcomers may read your post and think what you said is the way to go. NO IT IS NOT. If that were the case everyone who has a keen eye would be 'treating' most of the year! Oh yes, we should all be treating all the year, but selectively, as and when necessary. It's called IPM.

Why treat with a further chemical, which may affect spring build-up of the colony, if it simply does not need it? I am not a commercial beekeeper, and as such can monitor and treat each of my colonies on a rather more than 'blanket 'strategy.

Furthermore, your comment 'is only an indication of how many have dropped in the last half hour or so ' is also utter rubbish. Anyone with a modicum of common sense will know that. Speak up now, if there is anyone else out there that would do a mite drop count lasting only half an hour or so!

As far as I am concerned oxalic acid poses no threat to me. I have used it for more years than varroa has been around in the UK, probably twice as long.

If some are not entirely happy then don't use it. Be safe.

And I haven't got to F's yet.

Finman - think I said - 1pint water to 1 lb sugar-so 1:1 and tested by me- cos I used that method- and had a warrantable varroa drop with no bee loss. And I used 500ml of that syrup with 20gm OA

And Red Bee, I would definitely treat this winter.
I have never calculated mites. I have better to do.
in every hive they are hundres without calculating.
there is no harm to bees for oxalic handling.

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