Oxalic Acid Safety
Oxalic Acid Properties
Wally Shaw Document
Oxalic Acid Storage
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Oxalic Acid Dribbling Treatment Of Honey Bees Infested With Varroa

This method is applicable only in winter when the bees are both broodless and clustered. A mixture of Oxalic acid and sugar solution can be dribbled over them, causing direct damage to any varroa mites infesting the bees, at the cost of a small amount of damage to the honey bees themselves.

Making the solution...

Method of application

Trickle 5 ml along each seam of bees, using a syringe or a Perizin applicator if one is available. With small colonies 4 ml may be more appropriate per seam.

Total delivery of solution, should be about 30 ml for a weak colony or 40 ml for an average colony with a strong colony receiving 50 ml of the solution.

Temperatures recommended for treatment seem to vary from text to text, but are generally in the range 0°C to 5°C. However, the solution is warmed to room temperature (15°C) for application.

Treatment can be effected very quickly, with most colonies taking about a minute. Multiple or repeated treatment with oxalic acid by trickling should be avoided as the acid does cause some damage to the carapaces of the bees, which is cumulative and can result in colony loss.

Treatment results...

These results have been condensed from various papers, the most notable of these sources being Anton Imdorf, sometime in collaboration with others, notably J. D. Charriere and B. Bachofen.

Most reported figures are between 95% and 98.5%, certainly the average was more than 95%. The small residual numbers of mites form the breeding population for the following beekeeping season, luckily with such low survival rates the mite population cannot develop in a rampant fashion. However all of this is assuming that the weather is too cold for re invasions to occur from untreated colonies out of the control of the beekeeper.

Side effects of treatment

Odd weak bees can die due to the treatment, but numbers are usually single figures and if bees are weak, they are better out of the equation as they could be weak by virtue of disease.

because the trickling causes larger droplets than spraying of oxalic acid does, there is the potential for more carapace damage, hence the warning about non repetition of treatment to the same adult bees.

Here is a mail from Derek Steed...

From: Derek Steed [derek.steed@ngi.de]
Sent: Sunday, February 13, 2005 3:45 PM
To: irishbeekeeping@yahoogroups.co.uk
Subject: Re: [IBNewList] [OA] and provenance

Hello David, we use here the common dihydrate of oxalic acid. It is dissolved in a 50% sugar solution for the dribble method. Use distilled water or you will get a solution clouded with insoluble calcium oxalate. It's not too easy to dissolve, I use a mortar and pestle to get a fine powder and the sugar solution is warm. The amounts recommended here:

No. of colonies Sugar soln. Oxalic acid dihydrate
50,25 L9g
100,50 L18g
201,00 L35g

As oxalic acid is highly toxic one has to be very careful to thoroughly rinse away all traces of solid or solution, rubber gloves advisable. If you can't get oxalic acid in the UK you certainly can here from most apiary suppliers. I apply the hand warm soln. to the seams of bees, usually about 40 ml to a medium colony with 5 good seams of bees; I never use more than 50 ml even for a strong colony and never more than a single treatment.

Regards Derek

Sea also... Wally Shaw Document

Beekeeper Protection

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 poisenous to humans by ingestion.

Written... 26 October 2005, Revised... 17 August 2006,
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