Following a presentation by our club colleague Heinz at a recent meeting, I’ve had several conversations with other members about the use of sustained-release oxalic acid pads instead of the traditional oxalic acid vapor or formic acid strips. Many beekeepers across North America, the UK, Australia and New Zealand are trying these and the results have been favourable!
So my buddy Norm and I made up a batch! And appended below is an outline of Heinz’s recipe, Randy Oliver’s recipe (from https://scientificbeekeeping.com), and Norm’s and my “wisdoms” from our single experience. I hope this helps, and I look forward to hearing your experiences if you decide to use them!
Our monthly meeting is this coming Thursday, March 13th 6:30 p.m. – 8:30 p.m., at the Central Saanich Senior’s Centre, 1229 Clarke Rd, Brentwood Bay.
- 6:30-7:00 Beginner’s Corner Upstairs: Don L on Hive Equipment and Beekeeping Intro
- 6:30-7:00 Intermediates Corner Downstairs: Christina Klimaschka: Splits
- 7:00-7:45ish: Paul K from University of Guelph (Virtual): Buckfast Bees
- 7:45-7:55ish: Larry L: What to do this month
- 8:00-8:30: CLUB ANNUAL GENERAL MEETING
- Financial Reports
- Possible Membership Dues Increase: The Executive proposes an increase in annual membership dues from $32 to $35. Costs have gone up, and now over 90% of our members are renewing online, and PayPal retains $1.50 of each transaction. This must be approved or rejected at the AGM.
- Elections: The following positions are up for election:
- President
- Treasurer
- Second Vice-President
- Director at Large
- 8:30-8:50: Social time with Coffee/tea, cookies
Sustained release oxalic acid strips for mites
Treating hives for mites using oxalic acid (OA) vapour is a well-established practice, but it has limitations.
- It requires extra equipment; a vaporizer, battery, battery charger
- Any single vaporization is effective for only about 48-72 hours maximum, leaving time for the mites to regroup. It is commonly accepted that oxalic vaporization is effective for keeping mite counts down, but poorly effective for eradicating a full infestation.
- Using long-acting strips that stay in the hive addressed both these issues, and has already been shown anecdotally and in small studies to be as effective or more effective than vaporization and appears to be less toxic than formic acid. It has also been approved for use by the EPA in the United States.
- There is no build-up of oxalic acid in the hive and it does not contaminate the honey
NOTES
- You will need a well-ventilated space. Preferably do it outside; if indoors you will need an area with an extractor fan and plenty of windows and open doors. We did it outside and even then needed masks!
- While dry oxalic acid powder will not irritate, any moisture addition will enable the acid to cause significant skin irritation or burns. So DO wear gloves (dishwashing gloves, not flimsy latex or nitrile), eye protection, and old clothes in case of splashing.
- Have a bucket of water handy for rinsing gloves, spot rinsing splashes. Consider keeping a baking soda solution handy; 1 lb or 4 cups per gallon.
- If two or more people are doing this together, have one doing the ‘dirty’ work and one staying clean to move equipment, get things, etc.
- If making a batch of them, remember that during storage, gravity will gradually pull the glycerine downwards, soaking the bottom pads and leaching out the upper ones. So store them in a single layer, or max 2 deep and flip them periodically. You can put them in freezer for storage to prevent that, then thaw before use.
- The purpose of the glycerin is to absorb moisture from the air within the cluster, which then dissolves and activates the OA in the matrix. Once a strip goes ‘dry’ it is no longer effective.
Heinz Kaemmerer’s Recipe
Supplies
- Material for strips; felt or felted cotton, plotting paper or heavy-duty J-Cloths cut into strips of 1.25″ x 18″
- 100 ml vegetable glycerin (enough for ~7 strips or 1 hive)
- 15 g oxalic acid (weaker than Randy Oliver’s recipe)
Preparation
- Mix glycerin into small pot and gently heat to 50C-70C; do NOT exceed 70C
- Add oxalic acid and stir until it dissolves and liquid is clear. Remove from heat
- Lay the 7 strips in a single layer in a Zip-Loc bag and pour hot solution into bag and seal it, allow plenty of time for liquid to be absorbed
Application
- Drape the strips over the top bar of alternate frames at the front of the hive, make sure strips are not dripping then at the back of the hives drape strips on opposite frames.
- Four strips per brood box with 10 frames, 2 strips per nuc.
Note: From this recipe 100 ml glycerin (126 g) will soak 157.5 sq inches of felted fabric
Randy Oliver’s Recipe
From his site Scientific Beekeeping: https://scientificbeekeeping.com/instructions-for-extended-release-oxalic-acid/
Supplies
- Swedish dishcloths that are free of plastic mesh, or use felted cotton
- Glycerin (preferably vegetable glycerin)
- Oxalic acid powder
- Pot for mixing and heating oxalic powder and glycerine; preferably
- If making a larger batch, a shallow pan (aluminum roasting pan if good) for mixing final solution with the pads
- Zip-Loc bags to hold the finished strips
Notes
- Equal parts glycerin and oxalic acid powder by weight.
- Specific gravity of glycerin is 1.26, so 100 ml weighs 126 g
- For full efficacy roughly 55-60 sq inches of delivery matrix should be used if applied across (on top of) top bars, or 100 sq inches if draped over the top and down between the frames
- We found that 500 ml glycerin (630 g) made enough to cover 12 brood boxes each with ~56 sq inches matrix
- 100 ml glycerin = 126g, makes 10 strips of 2″ x 8″ and 4 strips do one brood box
- the glycerin/oxalic solution can be made indoors; don’t heat it up past 70C and remember oxalic acid is – an acid. Wear gloves and eye protection!
- Extra strips can be frozen for future use.
- The 1:1 solution is supersaturated and will crystallize at room temperature – so work fast while it’s heated! It’s okay for crystals to form on the pads; once pads are placed in hive the glycerin will absorb water from the atmosphere and the crystals will re-dissolve
Preparation
- Cut cloths into strips of 2″ – 2.5″ wide, depending on the size you bought. Remember you will need 50-60 sq inches per brood box.
- Get a bucket of water, or the baking soda/water mix, and place nearby.
- Mix the oxalic acid powder and glycerin in a small saucepan and heat gently just until oxalic acid dissolves and liquid becomes clear – do not heat above 70C (158F). While some people have said it can be done indoors, we found that even doing it outside on a camp stove made us run for masks!
- Pour some hot liquid over the strips; if doing a small batch put the strips in a single layer in Zip-Loc bags. If doing a larger batch, put a layer of strips in a shallow pan and pour a bit of solution over them, then add another layer of strips and pour more over top, etc. – just like making scalloped potatoes.
- Use gloved hands, quickly skoosh the liquid around and get it fully absorbed; you want them wet but not dripping. Work quickly, especially if working outside; the glycerin will cool quickly and the oxalic acid will start to crystallize, making it more difficult to spread throughout the strips. Give it plenty of time to be absorbed, a couple of hours or even overnight.
- Slip strips into Zip-Loc bags in a single or double layer; don’t layer more than this as glycerin will leach downwards by gravity giving a significant disparity between amount in the top vs bottom strips. You can freeze them until you need them and that could solve the gravity issue.
- Make sure the strips are not left open to the air; the glycerin will adsorb water from the air
- Place strips across top bars of frames containing brood in the brood box, 4 per brood box, 2 spaced near front of hive, 2 near back in a staggered formation
- Leave strips in place for 6 weeks (Randy Oliver’s test duration)