oxalic acid treatment

[Eric McArthur]

No it isn't.

75g oxalic acid dihydrate plus 1 kg sugar plus 1 litre water gives a volume of around 1600mls. I have a more accurate figure somewhere, but I'm short of time right now.

Those ratios give you:

4.5% oxalic acid dihydrate (w/v) in 1:1 syrup.

Which some folk prefer to express as the anhydrous equivalent of:

3.2% oxalic acid (w/v) in 1:1 syrup.

Both figures have been used in the literature, both are valid as long as you state the full details. Not 3.5%. The recipe above is the standard one. Some people deliberately reduce the concentration, some think that they are but they aren't, and people on forums everywhere argue that some other figure applies, but it doesn't.

all the best

Gavin

Hi Gavin
Do the calculation by weight!

Eric

[Rosie]

Eric

Like you I think the percentage should be expressed in weight/weight but for some reason the scientists insist on quoting the bastard proportions of w/v, which to me is both unscientific and idiotic. However, we are stuck with it and when I did the sums some years ago I came up with figures that were similar to Gavin's. Having said that, I also found other sugar concentrations (60%) can be used and concentrations as low as 2.4% w/v anhydrous oxalic acid can also be used almost as effectively. Hence I err on the lower side, especially as I believe that we will never find a bee that can cope with varroa if we continue to blast them all to kingdom come with powerful acids. Lower concentrations must also be better for the poor bees.

I am not trying to persuade others to switch to my methods but my experience does show that the concentrations are not critical.

Rosie

[Calum]

the german recipe is 3,5%
200g sugar
35g oxalic acid dihydrate
,75l water
mixed till disolved, top up to 1 liter
apply luke warm 30ml for a weak colony to 50ml for a strong one (or 5ml per bead)

[gavin]

Hi Gavin
Do the calculation by weight!

Eric

It is certainly possible to do the calculation by weight - and I think that chemists may prefer that way - but the solutions were produced up by biologists and biologists are happy with (w/v) concentrations. So that is how the oxalic concentrations have been presented.

all the best

Gavin

[Eric McArthur]

Hi All
]
Good discussion!

These are my thoughts!

Gavin wrote:
75g (71.4 g dry weight) oxalic acid dihydrate plus 1 kg sugar plus 1 litre water gives a volume of around 1600mls. I have a more accurate figure somewhere,
Those ratios give you:

4.5% oxalic acid dihydrate (w/v) in 1:1 syrup.

Which some folk prefer to express as the anhydrous equivalent of:

3.2% oxalic acid (w/v) in 1:1 syrup.
‘’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’’ ’’
The old adage of wood and trees seems to be relevant here! The amount of active ingredient is the critical – how the percentages are arrived at is purely speculative and seemingly irrelevant. See below!
In order to bring perspective to the discussion; let’s look at the big picture. We are dealing with a fixed quantity of crystal (71.4g); a fixed quantity of water ( 1000mls) and sugar(1000g). The water and sugar results in a solution of circa 1600mls, in which is dissolve 71.4 g of crystal oxalic acid dihydrate (active ingredient!).
Jon kindly did the sums and calculated that the 1600 mls would produce 32 - 50 ml treatments Each of these 50 ml treatments will contain, 71.4/32g of oxalic acid dihydrate = 2.23 g (active ingredient!).
Thus a strong colony in a single brood box covering 10 frames will receive a total of 2.23g in 10 x 5 ml trickles.
Consider the Ian Craig, 16 - frame double brood box example mooted earlier and the “accepted wisdom” of only trickling the top box in a double brood set up:
Consider 7, “between frame” spaces occupied by bees; each space received 5mls of solution; a total of 35 mls of solution is delivered. A quick calculation of the amount of active ingredient delivered indicates that only 2.23/50 x 35 = 1.56 g of active ingredient is delivered. This is quite a short fall.
Treating with the organic acids is, as experienced beekeepers know, not an exact science, and to blindly adhere to dogma in the face of novel situations can be unwise.

In any double brood box scenario there is a real danger of under -dosing if only the top box cluster is considered.

Eric

[Jon]

Eric. the maximum recommended dose is 50ml irrespective if there is one brood box or two and irrespective of whether there are 10 frames covered with bees or 15.
If you say more is needed, you are using your own guesstimates again rather than following published research.
I know which I prefer.
If you read some of the references posted in this thread, some of which you posted yourself, you will see that the most critical factor is having the Oxalic solution at a high enough concentration, strong enough to kill mites but not too strong as to damage the bees. ie concentration is more critical than volume.
It doesn't matter if you just trickle into the top brood box in a double system as the bees work the Oxalic right through the colony as they clean it off each other.
The other point to note is that if a cluster is divided between the top box and the lower box, splitting it in December would be a disaster.
Who in their right mind would want to split a cluster of bees in mid winter?
Applying Oxalic is an invasive process in itself but splitting a cluster is not a good idea.

Treating with the organic acids is, as experienced beekeepers know, not an exact science, and to blindly adhere to dogma in the face of novel situations can be unwise.

The problem is those who blindly adhere to novel solutions, the beekeeping tinkermen.

[Calum]

Hi Jon,
I do not like doing it myself, but alot of beekeepers here split the box to apply the oxalic solution to make sure they get it on the cluster.
- If the cluster is between boxes they just carry on and apply the solution to the lower box half of the cluster.. The risk is crushing the queen when closing the box but they all assure me she does not hang about in the open.

It is very invasive but it is done in under a minute.

[Jon]

Hi Calum
It's academic for me anyway as I keep Amm type bees and they never need more than a single brood box to overwinter.
I have heard beekeepers claim that it is unnecessary to split the two boxes as the bees work the oxalic right through the cluster during the cleaning process.
Carnica, Buckfast and Ligustica may well need a second box as they are much more prolific.
In December when I did the oxalic treatment the average colony size was about 6-7 seams of bees although one cluster was over 10.

[Calum]

Hi Jon,
all my productive colonies overwinter on two brood boxes (carnica).
The half of my nucs ran out of space in August so they also got another brood box that they filled up with balsamine..
There are various pros and cons for me on the two brood box front.
I like that they have plenty of space to keep plenty of stores in.
Also they are usually in the upper brood box completely by mid march so I can remove the now empty lower one and sort out the old comb and replace it with 50/50 fresher drawn out comb from the honey room and foundation. That way I have a good flow of wax in the colonies to prevent possible build ups of foul brood spores/ nosema / pesticides in the cold comb.

[EmsE]

I would have thought it was irrelevant whether they were in a double brood system or not as the size of the cluster would be the same, it's just that they've munched their way up the stores in the frame quite quickly (or not had enough).

I'm on a double brood and when applying the oxalic acid all the bees were in the lower box. If I hadn't provided adequate stores, the bees had moved up and the cluster happened to be spanning the 2 boxes, that couldn't justify doubling their medication, surely, as the cluster would still be of the same size.