For info, this is what I wrote for our State newsletter several years
ago. The research came from Europe and found that OA works best within a
range and is harmful above that range and ineffective below it. Since
this might have changed, it is provided with caution, but it is what I
used and was effective. Remember, I wrote this for Maine Beekeepers.

Part of the article is below my sig.

Bill Truesdell
Bath, Maine

The research papers I read which trialled Oxalic Acid drip method found
it works within a set range of concentrations. Their recommendations are **

*Composition of the solution: *35 g oxalic acid dihydrate in 1-liter
sugar syrup 1:1

*Quantity: *30 ml for a small colony

40 ml for a medium colony

50 ml for a large colony

This quantity corresponds to 5 – 6 ml for each occupied bee-space of a
Dadant or Swiss hive.

*Time of treatment: *In broodless colonies (November – December)

*Remarks:*

· only *one *treatment in autumn

· drip the solution directly on the bees between the frames

· treat with lukewarm solution

· perform the treatment at an ambient temperature above 0o C

· use only freshly prepared solutions or solutions that have been stored
for max. 6 months at

a maximum of 15o C (New info says do not do this but prepare new
solution for each use, and I agree)

· under certain conditions, drip treatment with oxalic acid may slightly
weaken the colonies in spring.

The spray treatment with oxalic acid is better tolerated by the bees (30
g OA dihydrate / liter water, 3-4 ml per occupied frame side)

· wear gloves and safety goggles during the treatment

The drip method was over 90% effective in killing Varroa.

My comments on the research:

Preparation: The solution is prepared using one liter of water with one
kilogram of sugar and 70 grams of store bought Oxalic Acid (which is
Oxalic Acid Dihydrate). Mix thoroughly. (For those still helplessly
addicted to pints and pounds and who do not need a quarts worth of
solution, use one pint of water, one pint of sugar, and 1.168 ounces of
Oxalic acid (same as about 2 1/3 tablespoons, or 7 teaspoons, or 2
tablespoons plus 1 teaspoon- all level and be precise) This is enough to
treat about ten hives).

Application: I use a 150 or 100ml syringe, which you can buy at many
farm supply stores, and drip 5ml of the mixture from end to end between
frames for each hive body (or frame of bees). Trickle down 5ml of the
solution by slowly pushing down on the syringe plunger. Do not be in a
hurry or it will squirt out and not drip out.

When to apply: In the fall when the colony is near broodless. You can
apply it down to freezing temperatures, so it is excellent to apply in
November.

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