Disease Treatment - Oxalic Acid
Oxalic Acid (C2H2O4), also known as ethanedioic Acid, Oxiric Acid and Oxalate among others, is a dicarboxylic acid, an organic acid that is commonly found in plants and vegetables such as Oxalis spp. various Brassica spp. It is widely used in various manufacturing and industrial processes including as a dyeing mordant, a chemical reagent, in rust removal, stain removal, polishing marble, bleaches and in photographic film development.
Note: Oxalic Acid is an odourless white solid that mixes with water. It is toxic in it's solid state and is harmful through inhalation, ingestion, skin and/or eye contact.
When heated, Oxalic Acid Dihydrate crystals sublimate (turn from solid to vapour) at 157℃ giving off a visible white fog with the same toxicity as described above. Remains heated beyond 189℃ will degrade to carbon dioxide and formic acid. See the hazards page for notes on the correct PPE required when sublimating OA.
Uses in Beekeeping
Oxalicic acid is a soft chemical that is effective against phoretic (on bees) varroa mites. It is a constituent in various varroa control products currently available in the Uk and approved by the Veterinary Medicines Directorate (VMD) e.g. Api-Bioxal, Varromed, Oxuvar Powder and Solution, Dany’s BienenWohl Powder and Solution, Oxybee.
Sublimation (Fogging)
Sublimation with Oxalic Acid is widely practised due to it's efficacy on phoretic mites. As it vaporises it fills the hive with a fog of Oxalic Acid residue which settles on the bees and hive components. The residue kills the Varroa mites on contact. Research carried out by Francis LW Ratnieks and Hasan Al Toufailia, Laboratory of Apiculture and Social Insects at the University of Sussex, detail how significant control of phoretic mites can be achieved.
Used as part of an IMP (Integrated Management Plan) varroa control is achieved by sublimating oxalic acid during broodless/lowest brood periods using a sublimation device and prescribed amount of Oxalic Acid Dihydrate.
A simple to use 12 volt 150 watt sublimation wand. Ideal for use with a 12 volt car or leisure battery. Gets very hot very quickly. Full vaporisation takes only 3 minutes. Care should be to taken to ensure it does not touch the underside of the frames during treatment, and when handling the hot wand.
Recommended Treatment:
- Treatment is only effective on phoretic (on bee) mites. It does not penetrate cell cappings.
- Can be carried out any time to reduce mite load. For maximum effect carry out when there is the least amount of sealed brood present e.g. End of December / beginning of January.
- Remove any honey supers before treatment.
- Dosage - sublimate with 2.0 - 2.5g OA per colony, repeated after 14 days to cover hatching brood.
Prerequisites:
- Windy days should be avoided.
- Correct PPE should be worn.
- Have all equipment ready to hand before starting.
- Remove any honey supers before treatment.
- Bees should be in the hive and not flying.
- Hive entrances should be suitably reduced to stop bees escaping during treatment.
- Close or seal any open floors and crown board vents for maximum effect.
Procedure
- Only use proprietary equipment and follow manufacturers instructions.
- Use the correct dosage of OA i.e. 2.0 - 2.5 g per hive.
- Keep the hive entrance closed for a further 15 minutes following treatment to allow fog to settle.
- Following same procedure repeat the treatment after 14 days to catch hatching brood.
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