HomeBeekeepingDirections for extended-release oxalic acid

Directions for extended-release oxalic acid

Prolonged-release oxalic acid for varroa administration

This methodology of software of oxalic acid is just not but authorized by the EPA.  Nonetheless, EPA doesn’t require an Experimental Use Allow for a restricted variety of hives.  Test along with your State Lead Company.


Though oxalic acid is just not as reactive as stronger mineral acids, it will probably nonetheless trigger eye injury, and if left on the pores and skin, tissue injury.  At all times put on security glasses and waterproof gloves throughout preparation, and watch out to keep away from splashing.

After preparation or software, wash your fingers and tools with cleaning soap and heat water to take away any acid residues, or higher but, neutralize any acid on fingers, hive instruments, or smoker with an answer of 10 heaping tablespoons of baking soda per gallon of water.

Dosage and supply matrices

For extended-release software of oxalic acid, it may be dissolved into glycerin, and utilized to the hive by both laying pads throughout the highest bars (if utilized between two brood chambers), or by hanging strips excessive bars, extending down into the interspaces between the frames.  The supply strips or pads have to be utilized in order that bees freely contact the surfaces.

Biodegradable cellulose matrices reminiscent of cardboard (chipboard), Swedish sponges, or cotton absorbent materials could also be used.  For full efficacy, roughly 55 sq. inches of supply matrix have to be used if utilized throughout the highest bars, or 100 sq. inches if hung between the frames.  The directions under are for moisturizer-free Swedish sponges, which maintain 100 g of 1:1 (weight to weight) answer of oxalic acid dihydrate to glycerin.  Different matrices, or completely different ratios of acid to glycerin, would require completely different preparation.


For extended-release software, oxalic acid could be dissolved in glycerin, absorbed into any variety of absorbent matrices.  Subject information counsel that for a double-deep hive, there needs to be roughly 60 sq. inches of matrix, holding roughly 100 g of 1:1 OA:glycerin (weight to weight), though different ratios could also be used (the upper the ratio of glycerin, the extra quickly the OA is dispersed upon the bees, generally with opposed results).  For cardboard strips to be hung excessive bars, it would require extra whole floor space to carry the identical quantity of answer.

To arrange sufficient Swedish sponge pads to deal with 10 full-sized colonies in double deep packing containers:

  • First put together the sponges by chopping them in half (into 3½” x 8” pads), every of which is able to take in 50 grams of the answer (50 g oxalic acid dose per hive).
  • Put on security glasses and waterproof gloves when making ready the answer. Have a neutralizing answer of 10 heaping tablespoons of baking soda dissolved in 1 gallon of water available, to neutralize any spills.
  • Place 500g OA dihydrate into a stainless-steel pan, then add 500g (400 mL) vegetable glycerin (add the glycerin second so as to keep away from splashing of the answer).
  • Place the pan over a low/medium warmth (ideally utilizing a double boiler), and warmth the components whereas carefully monitoring the temperature, to not exceed 160°F (the acid crystals will dissolve at as little as 110°F, and begin to bubble if the temperature exceeds 170°F).
  • Sometimes stir gently till the acid crystals are fully dissolved and the answer is totally clear. At that time, take away the pan from warmth.
  • Whereas the answer remains to be scorching, both (A) add twenty (20) (3½” x 8”) absorbent cellulose pads (or fifty (50) 1.25” x 15” cardboard strips) on edge into the pan and permit them to soak up the answer, or (B) place the pads right into a separate plastic container and slowly and thoroughly pour the still-hot answer over them. With both methodology, you might want to make use of tongs to fastidiously flip the pads over to acquire full absorption (which should happen earlier than the answer cools).  Watch out to keep away from splashing of the answer.
  • If all the answer doesn’t take in, the surplus needs to be drained off earlier than permitting the pads to fully cool. For simpler dealing with, enable the pads to chill for not less than a day earlier than software. The oxalic acid will recrystallize throughout this time, and make the pads simpler to deal with and apply, with no dripping of answer (beneath situations of excessive humidity, the pads will take in moisture and will not “dry out”).
  • The pads could be saved in a labeled sealed container for as much as 2 months, by which era the cellulose will slowly begin to degrade.


  • Optimum timing of this remedy in remedy rotation is to use the pads into the brood chamber at time of placement of the honey supers. This remedy ought to solely be used as soon as whereas colonies are rearing brood, rotating with miticides with different modes of motion, reminiscent of formic acid, thymol, amitraz, or fluvalinate.  An oxalic dribble or vaporization can then be used throughout the winter brood break.
  • Put on waterproof gloves.
  • Utilizing gloved fingers or tongs, apply two pads between the brood chambers, positioned in order to be throughout the cluster (keep away from putting beneath a high feeder the place syrup might spill, or straight towards pollen substitute). Placement of the pads should enable for motion of the bees over each surfaces.  The pads or cardboard strips will also be hung excessive bars, inserting them unfold between the 2 brood chambers.  For cardboard strips, 3-4 will likely be wanted per brood chamber.
  • For optimum efficacy, the pads should stay within the hive for 60-75 days, or till many of the acid has been distributed. After remedy, take away the pads, dealing with them fastidiously, since they’ll nonetheless include acid.
  • After removing, place the spent pads right into a plastic bag or container for transport, and rinse your fingers, hive device, and smoker with neutralizing answer.
  • Get rid of the spent pads in a landfill, or compost them.


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