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Know Your Product

OXALIC ACID

Oxalic Acid is a new treatment on the US market that has many beekeepers interested. Despite its recent approval in the US for managing varroa mites in honey bee colonies, it has been widely used in Canada and Europe for several years as an effective treatment. Many beekeepers are turning toward Oxalic Acid because of its low price and an efficacy of 95%+.

The most effective time to treat a hive with Oxalic Acid is when a hive has little to no sealed brood. Oxalic acid will only affect mites that are phoretic and not those in the reproductive phase found in capped brood; therefore, Oxalic treatments with capped brood will have no effect on the next generation of mites emerging with young bees. Treatments in the spring or summer can be accomplished by generating brood breaks or on packages and swarms when no brood is present. A Fall/Winter treatment is ideal as this is a natural brood break for the colony

There are three approved methods to treat with Oxalic Acid:

Solution Method: Dissolve 35 grams of Oxalic Acid in 1 liter of a 1:1 sugar to water mixture (weight:volume). It is easier to dissolve oxalic before adding the sugar. Smoke bees down from the top bars and use a syringe or applicator to trickle 5 ml of solution onto bees in each occupied bee space within each brood chamber. Use no more than 50 ml per colony whether the bees are in a NUC, single or multi-story brood chamber. Under certain unfavorable conditions (e.g. weak colonies, unfavorable overwintering conditions), this application method may cause some bee mortality or overwintering bee loss.

Vaporizer Method: Apply only to outdoor colonies with a restricted lower hive entrance. Seal all upper hive entrances and cracks with tape to avoid escape of Oxalic Acid vapor. Smoke bees up from the bottom board to help prevent bee mortality. For each brood chamber, place 1g Oxalic Acid into vaporizer. Follow the vaporizer manufacturer’s directions for use. Insert the vaporizer apparatus through the bottom entrance and ensure entrance is sealed. Apply heat until all Oxalic Acid has sublimated. Best practice is to leave vaporizer in hive a few minutes after disconnecting from power source.

Spraying Package Method: Spray broodless package with 1:1 sugar water solution (without Oxalic Acid mixed) at least 2 hours before spraying with Oxalic. This fills their stomachs to reduce ingestion of Oxalic Solution. Mix 1:1 ratio sugar water with 35 grams of Oxalic Acid (same ratio as Solution Method). Use 3 ml of solution per 1,000 bees. For a 2 lb package, use 21mL of solution. For a 3 lb package use 31mL solution. Apply solution evenly on both sides of the package. Store bees in a cool darkened room for 72 hours before hiving.