In an attempt to try and put together in a single thread, question (and answers about OAV) see below...
Oxalic Acid Vaporization – Questions and Answers:
What is Oxalic Acid?
Specifically: Oxalic acid is an organic compound with the formula H2C2O4. It is a colorless crystalline solid that forms a colorless solution in water. In terms of acid strength, it is much stronger than acetic acid. Typically, oxalic acid occurs as a dihydrate (containing 2 molecules of water) with the formula H2C2O4·2H2O.
Where is Oxalic Acid found?
OA is found in peanuts, pecans, wheat bran, spinach, rhubarb, beets, beet greens and chocolate. Some others include soy foods, sweet potatoes, black tea, berries and other dark leafy greens, like Swiss chard and collards. It is what gives food that “bitter” taste.
What happens to Oxalic Acid when heated (vaporized)?
When OA reaches 215 degrees (f) the water boils off leaving anhydrous (water free) OA crystals. At 315 degrees the OA crystals start to sublime (go from a solid to a gas). At 372 degrees, OA which has not sublimed decomposes to form formic acid and carbon monoxide. Although for the last, I'm trying to find out if this will only occur under "lab conditions."
How does Oxalic Acid kill mites?
The jury is still out. It is thought that OA vapors enter and destroy the cuticles thus rendering them footless. It is also thought that it destroys parts of the mite’s mouth. However it works, it decimates mites.
Is Oxalic Acid Safe for my bees and will it contaminate my comb?
When used as directed, OAV does not harm the queen, bees or the brood! And it does not contaminate the comb as poisons do. There are naturally occurring levels of oxalic acid in a hive. While OAV elevates that level, the hive returns to pre-treated levels shortly after treatment.
How much Oxalic Acid is used in the OAV process?
The recommended dosage is one gram per brood chamber. Most have two brood chambers, so use two grams (which is very close to ½ a teaspoonful. You could use a ½ teaspoon measure in lieu of two one gram (¼ teaspoons).
How is Oxalic Acid Heated for use in beehives?
Mostly, a 12 volt, 15 amp vaporizer is used. The OA is placed in the vaporizer’s pan which is then inserted into the beehive and connected to the battery. When the current is connected to the vaporizer, it heats the pan thus vaporizing the OA.
How long does it take to vaporize OA?
Some vaporizers take 2.5 minutes to vaporize OA, others less. The current is disconnected after the time limit and the vaporizer remains in the hive another minute to finish vaporizing. One should “test fire” their vaporizer prior to using as batteries in various states of age may take longer. Also, if one were to vaporize several hives (using a vaporizer not connected to continuous charger (such is in a running vehicle)), vaporization will start to take longer and longer as the battery degrades.
Do I have to seal the hive when vaporizing?
Yes, although a “perfect” seal is not necessary. During the vaporization period, the hive is sealed and once the vaporizer is removed, the hive resealed for an additional 10 minutes.
Is Oxalic Acid safe for the beekeeper?
Yes, if the beekeeper takes adequate safety precautions. Keep a smoker lit in the beeyard and stand up-wind. Do not BREATHE the vapors! The EPA is stating that an acid gas vaporizer is sufficient. In Europe a mask with an N95 particulate rating is the standard. OA vapors very quickly re-crystallize to cover all the surfaces in the hive making the breathing of the vapors unlikely. However, there is always the chance, error on the side of safety!
What is the outside temperature range to perform OAV?
You need an outside temperature of 37 (f). There is no top temperature. The temperature of 37 f is only needed at time of treatment and 1-2 hours thereafter.
Will the mites grow resistance to OA?
Since OA is an acid vs a poison, highly doubtful. OA has been used in Europe for 20+years and there is no reported resistance.
When is the best time to utilize OAV?
The very best time to use OAV is when the hive is broodless. Why? OA only kills phoretic mites - those on the bees, not in the brood. At that time OAV will kill an amazing greater than 95% of the mites in the hive! So when is the hive broodless or almost so?
1. At the beginning of winter (for many, somewhere between Thanksgiving and Christmas).
2. When you’ve hived a swarm.
3. When you’ve completed a split and removed most of the capped brood.
4. When you purchased a package and have placed it in a hive.
Another great time to use OAV is in late August/early September when the mites are out-breading the bees. What you are doing at that time is killing the mites that are emerging with brood and before they enter another brood cell about to be capped. During this time, you need to vaporize 3 times at 5 day intervals.
If you have high mite loads year going into spring your can do a series of treatments before you add your supers, however other treatments are better suited to treat hives that are heavily rearing brood.
Can I perform OAV with supers in place?
No, you must remove them or place a barrier between the brood nest and the supers. Cardboard or coroplast serve well as a barrier. You can replace the supers or remove the barrier two hours after treatment.
Can you use an extension cord on your OA vaporizer?
Yes, after you’ve made the necessary electrical connections. However, you should use a 14 gauge wire on your extension cord to keep the current from dissipating thus making vaporization take longer. You can also use several vaporizers together for faster treatment of multiple hives.
Is Oxalic Acid legal to use in the US in beehives?
Not yet, but very soon. The EPA will soon allow its use. There will be no need for individual state approval once it is approved.
As other questions are posed, I’ll add them (and the answers) to this list.