treating honey bee colonies for varroa

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Page 1Treating Honey Bee Colonies for

11/5/2012 1:16:03 AMhttp://www.honeybeeworld.com/diary/articles/drip_incl.htm

Treating Honey BeeColonies for Varroawith Oxalic Acid Drip

(Drizzle Method)Note: This page is inserted automatically several places on the site and as a stand-alone pagewhich I update from time to time. That will explain future events appearing in the past record

Click on pictures to enlarge

The 'Optimiser"from Medivet

The Gun

Gun Setting Indicator(mL per stroke)

Medivet's

InstructionSheet

Drip MethodInstructions

In 2008, to treat 10 colonies, I measured 250mL of sugar and 250mL of water.They weigh about the same. When I mixed them, I got a little over 400 mL ofsyrup. That was the most uncertain part of the task. I then calculated thecorrect amount of dihydrate for 400 mL and mixed it up. It did not seem toharm the bees and they did well in 2009.

From that mixing experience, I conclude that to get around a litre of syrup, 20% more, or600mL of each sugar and water must be used.

To the resulting one litre of 50/50 syrup, add 35 grams of oxalic acid dihydrate. The acidshould be weighed, since volume is variable. Pre-dissolving the acid crystals in a small

amount of water after weighing and before mixing into syrup is recommended

Here is the complete Canadian oxalic label. (relevant excerpt below).

SOLUTION METHOD

NOTE: To completely dissolve oxalic acid dihydrate, use warm syrup. Dissolve 35 g ofoxalic acid dihydrate in 1 litre of syrup made from a 1:1 sugar : water (weight:volume)mixture of sugar and water. Smoke bees down from the top bars. With a syringe or anapplicator, trickle 5 mL of this solution directly onto the bees in each occupied bee space

in each brood box. The maximum dose is 50 mL per colony whether bees are in nucs,single, or multiple brood chambers. Under certain unfavourable conditions, e.g., weakcolonies, unfavourable overwintering conditions, this application method may causesome bee mortality or overwintering bee loss.


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Here is the complete Canadian oxalic label. (relevant excerpt below).

SOLUTION METHOD

NOTE: To completely dissolve oxalic acid dihydrate, use warm syrup. Dissolve 35 g ofoxalic acid dihydrate in 1 litre of syrup made from a 1:1 sugar : water (weight:volume)

mixture of sugar and water. Smoke bees down from the top bars. With a syringe or anapplicator, trickle 5 mL of this solution directly onto the bees in each occupied bee spacein each brood box. The maximum dose is 50 mL per colony whether bees are in nucs,single, or multiple brood chambers. Under certain unfavourable conditions, e.g., weakcolonies, unfavourable overwintering conditions, this application method may causesome bee mortality or overwintering bee loss.

Other resources:

Scientific Beekeeping

Oxalic Solution Storage

An email rec'd Nov 29...

> I've been working on reconciling various OA formulas and was using your

site (Nov 18-19 2009 diary) to figure the weight of 1:1 syrup. So I had to

figure out the cause behind your statement: "Well the best-laid plans... I

mixed as above and came up with 1,600 mL, not the expected amount,..." on

Nov 19. The cause was your calculation 4x400=1800 behind your statements in

the previous paragraph.

Thanks. You are right. That explains it.

> I had been concerned that you were not getting consistent syrup weights

from mixing weighed ingredients. The underlying physics appears consistent,

so I am comfortable now.

> Another surprise is that the Canadian label produces a much weaker

solution than what Randy Oliver is recommending on his web site. Randy's

1:10:10 by weight looks to me to be nearly twice the strength you used.

There tends to be confusion between the acid concentration in water and the amount of dihydrate

required to achieve it. The dihydrate already has two water molecules attached, so a considerably

greater weight of dihydrate is required than would be the case if pure acid were used. I am not

aware of sources of the pure acid, and there is no need to use pure acid if the fact that the dihydrate

contains water is taken into consideration in the mixing.

A Persistent Confusion(note: The info below was corrected Dec 1/09)

There tends to be a persistent confusion confusion between the actual resulting acidconcentration in water and the amount of the dihydrate required to achieve it. Thisconfusion is likely due to the fact that the process has been developed by people with somechemical training and is practiced by people who may be less conversant with chemical


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chemical training and is practiced by people who may be less conversant with chemicalmatters, or who have been out of school a long time.

From Wikipedia

Oxalic acid is the chemical compound with the formula C2O2(OH)2 orHOOCCOOH. This colourless solid is a relatively strong carboxylic acid, being

about 3,000 times stronger than acetic acid... Typically oxalic acid is obtainedas the dihydrate. (emphasis added)

As can be seen in the figure below, the dihydrate contains two molecules of water andweighs much more than the actual oxalic acid it contains. The calculations below simply addup the weights of the atoms in each and show how much of the weight in 86 grams of thedihydrate crystals we buy is actually acid (90 g) and how much is water (36g).

Molecular formula C2H2O4 (anhydrous)Molar mass 90.03 g/mol (anhydrous)

Molecular formula C2H2O42H2O (dihydrate)Molar mass 126.07 g/mol (dihydrate)

From the above, we can see that to get the same 90 grams of oxalic acid, 126grams of the dihydrate crystals must be used, compared to 90 g of the pure stuff

-- thus the confusion.

Since the amount of acid used is very small compared to the water in the syrup, the 'waterof hydration' may be ignored when calculating the water in the total solution, but since thewater in the crystals is insignificant compared to the totalwater in the syrup, but since it is

almost half the weight of the crystals, it must be considered in measuring the acid.

Still confused? Some very intelligent people get mixed up by this problem. It is a good thingthat there is a label that spells it out in simple terms. Follow the label and all should go well.

Be sure to double-check, though. You can see the obvious addition error I made.Fortunately, it was minor, and in mixing the syrup, but it shows how checking andrechecking can pay off.

treating honey bee colonies for varroa

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