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HomeBeeKeeping2022 Prolonged-Launch Oxalic Replace: Half 1

2022 Prolonged-Launch Oxalic Replace: Half 1

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2022 Prolonged-Launch Oxalic Replace

Half 1

Randy Oliver

First revealed in ABJ March 2022


As increasingly more beekeepers attempt to wean themselves off amitraz, there may be nice curiosity in oxalic acid.  Sadly, a dose of OA by any of the currently-approved utility strategies displays little residual motion, so has restricted efficacy if a colony is rearing brood.  Nonetheless, as with different miticides offered in extended-release strips or formulations, oxalic might be utilized in the same method.


My sons and I’ve experimented, by allow [[1]], with OAE for a while, testing a spread of ratios of oxalic to glycerin, in addition to with quite a lot of supply matrices.  Up to now, we’ve decided that:

  • We just like the dealing with traits and efficacy of the 1:1 (by weight) ratio.
  • Swedish sponges make a fantastic supply matrix, however are expensive.
  • OAE has the potential to take mite infestation charges all the way down to zero, however it’s a long-term remedy. It doesn’t trigger as speedy a discount of mite ranges as do most different therapies (formic is the quickest).  It requires about two months to exhibit full efficacy.
  • Very importantly, as a result of its sluggish motion, highest efficacy is attained in yards the place there may be little mite immigration.
  • Its efficacy doesn’t seem like affected by temperature or humidity (since broodnest setting is regulated by the bees).
  • It’s greatest utilized proactively (early within the season), quite than reactively (ready till the mite degree will get excessive).
  • It’s simple on the bees and brood.
  • It’s not a fear so far as contamination of honey or the combs.
  • Sadly, this utility methodology isn’t but authorised by EPA, and I under no circumstances encourage or endorse the usage of it with no correct allow.


Though this utility methodology of oxalic acid isn’t but authorised by our slow-moving EPA [[2]], it’s clear to me that it’ll be a recreation changer for varroa administration.  My sons and I are impressed by the way it has carried out in our personal licensed experiments. I additionally get studies from beekeepers in nations the place it’s authorised or allowed [[3]], in addition to from beekeepers elsewhere (Determine 1).

Fig. 1 Beekeepers from all around the world ship me glowing studies on how effectively OAE can work.  The pictures above are from an expert East Coast beekeeper (whom I assume is permitted), who waxed poetic about how OAE remedy resulted within the strongest, healthiest, and most honey-productive colonies in reminiscence, holding the mite ranges in his busting colonies to low ranges.  His pictures converse for themselves.

Sensible utility:  I’m not attempting to promote or promote this utility methodology (particularly because it’s not but authorised).  It’s not a panacea, and is greatest used proactively.  And as with different therapies, there are all the time outlier colonies during which mite ranges by some means don’t reply, and the remedy might not be capable of sustain with heavy mite immigration. 

However as a result of it will match very effectively into our personal industrial operation (since we eschew comb-contaminating artificial miticides), my sons and I proceed to carry out permitted analysis not just for  the advantage of the beekeeping business, but additionally in personal curiosity — and for  that of our poor bees, who beg for reduction from this parasite.  In the long term, OAE might assist us to stave off varroa till mite-resistant bees turn into broadly obtainable [[4]].


The idea of OAE is to offer sustained launch — from an inert supply matrix — of the oxalic acid onto the bees.  Glycerin acts because the solvent and provider of the acid, and likewise has some great benefits of being cheap, food-grade, a humectant (which helps the acid to be efficient), an adhesive (that helps the acid to stay to the bees), and has the additional advantage of being distasteful to the bees (so that they’re much less prone to devour the acid).  However what’s one of the best matrix to make use of?

I’ve scoured catalogs and shops for appropriate absorbent sheets or pads (ideally biodegradable), and gotten solutions from beekeepers in all places.  This spring I selected seven matrices to match to the profitable Swedish sponges (which work higher than do the store towels and cardboard that I’d beforehand experimented with).

I had bought numerous completely different manufacturers and shapes of cotton wipes and pads to strive, and determined to make use of the Q-tips model, because it had crimped edges.  As a result of they occurred to be spherical, for comparative testing I measured their floor space (4 in2), and minimize rectangular strips of similar floor space from the opposite matrices.

I ready six pads of every matrix, utilizing a single batch of OA/gly answer, after which allowed them to come back into equilibrium at a set temperature and humidity in an incubator.  After weighing the pads, beekeepers Brion and Alice Dunbar helped me to haphazardly place one pad of every matrix into every of six hives  (Fig. 2), and allowed the bees to stroll over them for 20 days (7 April to 27 April).

Fig. 2  With a purpose to decide how effectively every matrix dispersed the OA/gly answer onto the bees, we coated the highest bars of the decrease brood chambers of six hives with masking tape to stop absorption, and weighed the saturated strips earlier than and after 20 days within the hive. The yellow-starred matrices seemed to be essentially the most promising.

We then collected the pads, once more allowed them to come back into equilibrium within the incubator, and reweighed them as a gaggle with a view to decide the typical quantity of weight misplaced per pad (Desk 1).

Desk 1.  The examined matrices, ordered by weight reduction.  None misplaced as a lot because the sponges, however some have been shut. I’ve highlighted an important cells.

Three of the matrices confirmed promise, as a result of their quantity of absorption or launch, in addition to different traits (the bottom two had been eliminated by the bees).  So I made up a batch of them, together with some sponges (Determine 3).

Fig. 3 I ready the 4 matrices to be examined with the identical batch of OA/gly answer on the 1:1 ratio.  Tip: for full absorption, it’s necessary to offer any matrix sufficient room to broaden.

I then ran a quickie trial of the 4, testing them by seeing how a lot they elevated the speed of mite drop after utility (in 2 colonies for every matrix, randomly blocked by beginning mite rely) (Determine 4).

Fig. 4 In my preliminary trial of the 4 most promising matrices, I used to be sadly solely in a position to monitor mite drops for 5 days (16-Could was the pretreatment baseline rely). The cotton pads attributable to far the best short-term enhance in mite drop.

Wow, cotton pads seemed actually promising!  I had hoped that the bees would possibly tug the saturated cotton fibers off, and drag them down by way of the colony (Determine 5).


Fig. 5 The above photograph was taken after the pads being within the hive 10 days.  There didn’t seem like the quantity of tugging of the fibers that I’d hoped for.  Observe the slight propolization across the edges.

Sadly, the facial pads have been troublesome to separate after preparation, and would require 13 spherical pads to equal the floor space of a single Swedish sponge.  So I didn’t comply with up any extra with them this season.

Sensible utility:  Cotton in some type nonetheless stays a really promising candidate (I plan to strive terrycloth or different absorbent cloth, and plastic-free feminine-hygiene pads).  I additionally experimented with including thymol to the pads, but it surely didn’t seem to enhance efficiency.  Properties to contemplate with any matrix are its dealing with traits, together with preparation, discipline utility, and ease of elimination from the highest bars after remedy.


As I reported final yr [[5]], we had, in late spring and early summer time, utilized a quarter-sponge strip of OAE to a lot of colonies rising from nucs in experimental hives in a number of yards, and located {that a} minimal-dose remedy largely suppressed enhance in mite wash counts for a number of months.  So we have been curious as as to whether such a low-dose remedy would show to be efficacious in bigger low-mite colonies.  And primarily based upon our preliminary experimentation with the choice matrices above, I believed that we may run a single comparative discipline trial to reply three questions:

  • How do Swedish sponges, Maximizer pads, or acrylic felt examine in efficacy at decreasing mite masses?
  • Is there a minimal floor space (versus quantity of OA) of OAE pads obligatory to acquire good efficacy in double deeps?
  • Are you able to dose with OAE proportional to the mite infestation fee? e., can you employ fewer strips in a low-mite colony?

For experimentation, we had put aside a bunch of intentionally-untreated colonies with 2nd-year queens, grown from March and April nucs break up from colonies returned from almond pollination, in 4 completely different yards.  So in late Could — as their mite infestation charges climbed — I believed up an experimental design to try to reply the questions above.


Final yr we realized that one half-sponge decreased mite ranges considerably, and two half-sponges exhibited superb efficacy.  I figured that if we minimize the pads into strips the identical measurement as 1 / 4 of a Swedish sponge, after which apply solely a single strip to the lowest-mite hives, going as much as 4 strips for the highest-mite ones, that we may maybe fine-tune the optimum dose.

We began the trial by taking mite wash counts from all of the hives within the yards on Could 20-21, sorted them by beginning mite degree, and randomly assigned remedy sorts accordingly (Desk 2).

Desk 2. We sadly didn’t have many colonies with mite counts above 30, and looking back, I ought to have assigned the 4-strip remedy to extra colonies within the 11-30 mite teams.

Scientific observe: We randomly assigned the therapies, blocked by beginning mite rely.  We didn’t run any damaging Management (untreated) teams, since we have been testing for comparative, quite than absolute efficacy (and it will have taken eight Management teams).  In the event you have a look at the dates of all these experiments, you’ll be able to see that we have been performing experiments back-to-back in brief order, speeding in opposition to the season and mite buildup.  I needed to make fast, on-the-spot selections, and looking back generally want that I had finished one thing in a different way. 

We utilized the strips on Could 26-27 (Determine 6).  On June 30 we spot checked colonies for strip situation and mite wash counts.  At the moment level, the acrylic felt didn’t seem like performing, so we eliminated these colonies from the trial.

Fig. 6 In line with the beginning mite wash rely, we utilized from one to 4 1¾ “ x 7½ ” strips per hive after smoking the bees off of the highest bars.

On July 20 (after 55 days of remedy) we took ending mite wash counts.


The outcomes are proven in Figures 7 and eight — the extra blue you see relative to crimson means the extra efficacious the remedy.




Fig. 7  Opposite to our observations the earlier yr, making use of solely 1 / 4 sponge to low-mite colonies didn’t do the trick (too many had their infestation charges enhance considerably).  However much like final yr’s outcomes, two strips (a half sponge equal) decreased the mites, and a full-sponge equal  (4-strips) nailed it.  Observe that a number of the highest-mite hives went to counts of zero.

Sensible utility:  Once I shared the outcomes with my sons, it was clear {that a} 4-strip equal (two half-sponges) would now be our commonplace OAE remedy for full-strength colonies.


The outcomes for the Maximizers have been fairly much like these for the Sponges (Determine 8).


Fig. 8 It seems as if the Maximizers could also be barely much less efficacious than the sponges at low dose.  As with with the sponges, the 4-strip hive zeroed out.

Sensible utility:  As soon as a colony’s virus an infection will get too excessive as a result of having an elevated mite load, it might not be capable of be saved by any remedy.  I’ve been stunned that in our earlier trials, just about all high-mite colonies recovered if given an OAE remedy.  On this trial, one of many two highest-mite 4-strip colonies for every matrix kind didn’t make it, however the different one not solely survived, however ended up with a mite rely of zero!


Let’s check out the comparative impact of treating with both 1 or 3 strips of the 2 matrices.  To take action, I merely totaled the mite counts for all of the colonies in every remedy group in the beginning and finish factors (Determine 9).

Fig. 9 Observe that the 1-strip teams began with a lot decrease mite ranges, which went up, whereas the 3-strip teams began with a lot increased mite ranges, which then went means down.  The absolute reductions have been 91% for the Sponges, 90% for the Maximizers.  (n = 21 for 1-sponge, 12 for 3-sponge, 22 for 1-Maxi, 10 for 3-Maxi).

These absolute reductions (versus calculated efficacies) are fairly spectacular in their very own proper, however don’t keep in mind the anticipated enhance that would have been factored in had there been comparative knowledge from professional controls.

To legitimately calculate efficacy of a remedy, the Check and Management teams would want to begin on the identical infestation fee.   However an issue with testing varroa therapies is that with a excessive beginning rely, the Management colonies might succumb to the mite and virus load.

Sadly, one can’t simply begin the Management group with decrease infestation charges than the Remedy group, since my earlier knowledge point out that high-mite colonies are inclined to exhibit increased efficacy values than these for colonies with decrease beginning mite counts [[6]].  So I questioned whether or not that pattern held over the vary of beginning mite counts for the 22 hives within the two 3-strip take a look at teams mixed collectively (Determine 10).

Fig. 10  Correlations between the beginning counts and p.c mite discount from remedy for the 22 colonies within the two 3-strip teams mixed.  There was no obvious correlation.

In gentle of the above, and with the necessary caveat that any efficacy calculation for this trial can’t be thought of professional (as a result of Management group not beginning on the identical infestation fee), I really feel that it’s nonetheless informative to run the Henderson-Tilton calculation anyway, utilizing the 1-strip functions because the “controls.”  Doing so, the calculated efficacies are 97% for the Sponges, and 98% for the Maximizers!

Sensible utility:  The 90% absolute reductions, and admittedly-questionable 97% efficacy values are what we have been on the lookout for.  The much-cheaper Maximizers are trying fairly good!


  1. For full efficacy of OAE for mite management by utilizing an absorbent matrix laid throughout the highest bars between the brood chambers, it takes about 55 in2 of matrix holding 50 g of OA dissolved in 50 g of glycerin.
  2. We don’t but know whether or not it helps to divide the matrix, however bought good outcomes final yr with it divided into two items.
  3. Maximizer pads (Determine 11) are a lower-cost different to Swedish sponges, and are a bit simpler to scrape off the highest bars after remedy.
  4. We do know that strips can alternatively be draped excessive bars down between the combs with good outcomes, however I’ve not finished a lot analysis on this methodology of placement.
  5. My preliminary analysis, substantiated by latest work by Dan Aurell [[7]], signifies that Aluen CAP strips (10 g OA per strip), hung between the frames, requires greater than 4 strips for equal efficacy in a double deep.
  6. Aluen CAP makes use of a 1:2.5 ratio of OA to glycerin; we like a 1:1 ratio; New Zealanders sometimes use an intermediate dilution.
  7. Larger-glycerin formulations (and maybe cotton pads) launch the OA extra shortly, and might probably trigger short-term hostile results.
  8. We’ve realized lots to this point, however must proceed our analysis!

Fig. 11 A devoted paper cutter with a built-in clamp permits for fast reducing of matrices.  Listed here are ½-sponge equivalents of Maximizer light-weight pads, that are a readily-available different to Swedish sponges.

Replace:  That is solely a report on my experimental trials.  I don’t make any suggestions, so please don’t write me for such.  The Spilltech Maximizer pads above (Merchandise # GPC100S) include a little bit little bit of plastic fiber, and a flame retardant (that doesn’t seem like dangerous to the bees).  We examined the light-weight model, and can take a look at the heavyweight model this yr. 

To be continued…


Because of Brion and Alice Dunbar, my sons and crew of Golden West Bees, and to all of the beekeepers who’ve provided solutions and observations.


[1] Acquiring annually a Pesticide Analysis Authorization from the California Division of Pesticide Regulation.

[2] Me and some different beekeepers had a gathering with EPA’s Workplace of Pesticide Applications as I wrote this text in January.  I’ll write about it subsequent month.

[3] New Zealand very moderately has decided that beekeeper use of the natural acids for mite administration poses scant danger to the general public or setting, permits beekeepers to make use of them at their very own discretion.  Extra on this subsequent month…

[4] Extra on this in an upcoming article.  I simply returned from one in every of our outyards, during which 50% of the colonies have exhibited sturdy mite resistance this season, and required no remedy in any respect.

[5] Mite Management Whereas Honey is on the Hive: Half 3 – Scientific Beekeeping


[7] Pers. comm. and introduced on the 2022 ABRC.



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