# OAV Dosage - Legal Dose Not Enough



## psm1212 (Feb 9, 2016)

Watched a Zoom meeting last night put on by Auburn University Bee Lab that hosted Dr. Cameron Jack from the University of Florida Bee Lab. It is part of an educational series for beekeepers being sponsored by Auburn.

There are threads on this board regarding Cameron Jack's research released in January 2020 regarding OAV used in conjunction with brood breaks that had some fairly disappointing results for those of us that force brood breaks to treat with OAV. The study alluded to the theory that the legal limit of 1gram of OA per brood box may be insufficient to get an effective kill.

Last night, Jack revealed other trials that were being performed that were not covered in the January release, where hives were treated with 1g (legal dose), 2g and 4g with a control group that was not treated. Jack did not get deep into the details or numbers, but did show us a graph that shows a significant increased efficacy at higher doses and only nominal efficacy at the current legal dose. Jack also stated that there were little or no increased ill effects to bees, brood or honey in using the higher doses. He indicated that there was a current plan for Dr. Jack and Dr. Ellis (perhaps in collaboration with others) to build enough evidence to lobby the EPA for an increase in the legal amount of OA.

Of course, there was plenty of warnings and finger-wagging about "the label is the law" and do not let this information encourage off-label uses. I repeat them here in hopes we will not have pages of discussion about how we should all be adults and act in accordance with laws. 

The fact that the OA legal dosage set by the EPA is far too low has long been suspected, if not known. Even Canada, which we supposedly based our EPA approval, has basically twice the legal dose as the US. If there is such thing as resistance to OAV (I do not believe there is) the most certain way to create and promote that resistance is by inoculating mites with sub-lethal dosages of OA.

I am hoping that Dr. Jack publishes another paper on this portion of his study. Anybody seen anything?


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## Hobo (Mar 4, 2014)

Scott McArt discusses Cameron Jack's research and findings in the June 2020 issue of American Bee Journal in his article entitled: Notes from the Lab: The Latest Bee Science Distilled. Is oxalic acid vaporization and/or brood interruption effective at controlling varroa?


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## clyderoad (Jun 10, 2012)

Johno!, Johno!, Johno!


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## johno (Dec 4, 2011)

Well when the EPA tells me what they do with their bees I will start to take notice of what the EPA has to say. Of course OAV does not work, you can ask my bees that have been treated with nothing other than OAV for the last 6 or 7 years with losses of less than 10% over winters mostly from starvation I am sad to say. But I am at around 50 colonies at the moment and have been trying to get to no more than 25 colonies for the last 4 years or so. When I treat a normal hive of 2 deeps or 3 mediums I fill the silicone cap to the top and then will have a little dome of OA on top formed by my measuring spoon so I guess around 3 to 4 grams per treatment. Was just state inspected on June 3 and mite counts again came up at zero. But all my hives got around 12 to 13 treatments last year and nothing so far this year. What little honey I get will be removed in the next 2 to 3 weeks and then it all begins.


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## JWPalmer (May 1, 2017)

It is like deja vu, all over again. To refresh my memory, I just weighed out my standard dose which is a well rounded 1/2 tsp. Comes to 3.5 grams. This is what I use to treat a double deep brood chamber. Two years OAV exclusively and no mite related hive losses. I told Luke I had a few mites starting to appear on the bottom boards so we did not do a mite wash, just checked for diseases. He knows I will be starting treatments in a few weeks.


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## little_john (Aug 4, 2014)

It's a strange approach to have such a fixed-size 'legal' dose, when the volumes of boxes and the strengths of the colonies within them are variable. 
LJ (VOA only - many years with no issues)


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## Robert Holcombe (Oct 10, 2019)

Physics - Math units do not matter


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## Robert Holcombe (Oct 10, 2019)

I wonder how hte procedures and result compare with the following:

"A recent study at Sussex University examined the effectiveness of different doses and application methods on mite and bee mortality. The experiment involved 110 hives. The results showed sublimation (vaporization) was far better at reducing mite populations and showed no increase in bee mortality."

Will a peer review approve the Fla. data and will the two research projects support each other. How are different environment and seasonal effects included in the data or is it local in-situ applicable data? 

I personally have no problem with the "approved dosage". I have not checked the EPA label lately but I use 1 gram per brood box in my defined brood chamber of 2 mediums and deep. ( size of box is said to not applicable - Dadant, undefiend by EPA label). Thus I underweight at 2 grams, could use 3 grams, but get very good results. I confirm my results by counting dead Varroa dropped onto the sticky board after 3-4 days. 

Clearly or it seems to me, Florida has a different annual cycle than my northern, coastal environment. Brood rearing really never stops in Florida or so I have heard (Ellis) which is entirely different than my cycles. For sure I am nearly brood-less around Jan 1 when I perform my Winter OAV treatment to confirm the efficacy of Fall treatments to stop the Fall migration of mites (13,500 of them this past year). I re-treat if counts are not near nil or 0-5 dead drop count. 

I tried a brood break and OAV but it does not work during or before robbing season. Net performance result this year, 9 for 9 foraging again; one drone laying queen replaced. I find repetitive OAV during robbing season works well here until test data shows a real decline in phoretic varroa followed by a winter clean-up. My one hive I expected to die because of he unusual number of Varroa within - survived - weak coming out of winter but survived and building up well. 

So, I guess, this is a OAV - Brood Break specific recommendation? Also, I thought the USDA copied the Canadian approved process, including the "supers off" requirement. Have they increased the allowed rate since the EPA approval? I'll be looking for the ABJ June article.


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## Biermann (May 31, 2015)

Interesting. The debate goes on and on, but since I use OAV and no other treatment, 3 gram on double deep broods, 7x4 days apart in spring & fall, the mites are gone and I have had no loss last winter with ambitious hives waiting for field crops to flower. 

I see in our Prairie region, too, that the governmental smarties stick with the chemical warfare and don't even test OAV, while commercial Beek's with 4-12,000 hive switch. 12,000 double deeps x 4 strips x $3.50 x 2 per year= $336,000.

That buys a lot of man hours that have to visit hives anyway in spring & fall. 

OAV in clustered hives has not worked for me, but early fall and early spring with some brood has worked very well!

The OAV has to penetrate into the bee main 'congregation', laying on the cluster is a waste of effort, MHO.

We can discuss this till hell freezes over and still get the same questions. 

Habee Beekeeping, JoergK.


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## psm1212 (Feb 9, 2016)

Not sure I understand what scab got picked by the post. I don't think any serious researcher questions the ability of OAV to kill varroa mites and its potential to use it as a management tool. Perhaps even a complete solution. In 2015, when the EPA originally approved OAV for use in the US, the 1 gram per box dose struck most of us as very odd. How can 1 gram of OA treat a Deep box volume and a Medium box volume with equal efficacy? 3 seams of bees vs. 10 seams of bees? But we were all just happy to finally be pseudo-legal that we did not look the Brushy Mountain (RIP) gift horse in the mouth.

As to beekeeper experiences, I also used OAV exclusively. But by 2018 decided that I was still losing too many colonies to disease. I had much lower losses than published averages. It is not that exclusive OAV was not effective, just not as effective as I wanted. 

Like UF in Gainesville, FL, I don't have a winter. I have active brooding 12 months of the year. My swarm season starts around the last week of February. The exponential mite increase resulting from year-round brooding in the colony requires a much different management approach on the Gulf Coast than is required in areas of the country that actually see snow more frequently than once a decade.

In 2018, I began removing all of my honey supers by mid-July and inserting Apivar strips. I force brood breaks in all hives in early spring and use OAV at that time. I also treat with OAV between Thanksgiving and Christmas, when brood nests are smaller. If I don't starve them, they live.

So, this could change my thinking about OAV. If, in fact, the effective dose (at least for my climate) is 4X what I was using prior to 2018, maybe I can revisit the idea of eliminating Apivar from the treatment regimen. I was encouraged by the UF's research results. Not understanding the angst. Must have missed something in previous threads.


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## rbaillar (Jan 28, 2020)

I treated 20 hives with the legal limit of OAV December 2019 then Apivar early spring resulting in 0 mite problems. Now I'm not sure if it was OAV, Apivar or a combination. Now I'm interested in seeing data on increase volume of OAV.


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## johno (Dec 4, 2011)

I think we will all agree that if crystals of OA get onto a mite it will die, the length of time those crystals remain active in a hive is not quite clear although it has been said to be a max of 3 days. With those parameters in mind if brood is present in the hive treatments need to take place every 3 to 4 days to get good results. However the effectiveness of the treatment will depend on the crystal vapor reaching all areas of the hive and by increasing the dosage we will be loading the equation in this direction. Using the recommended dosage may provide this coverage in many hives but may not in others due to burr comb in places and also due to vapor leaks and as no adverse reactions to the bees has been seen it is better to be sure of your treatment than to have doubts of the coverage. I personally have no doubt that a 42 day treatment of OAV with treatments every 4 days will produce results equal to Apivar.


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## psm1212 (Feb 9, 2016)

johno said:


> I think we will all agree that if crystals of OA get onto a mite it will die, the length of time those crystals remain active in a hive is not quite clear although it has been said to be a max of 3 days.


That is a crucially important qualifier that you make. I have never found (and do not think they exist) good studies on the post-application efficacy of OAV. Just a lot of conjecture. The conjecture (from reputable folks on both sides) seems to run from OAV being nothing more than a flash treatment with efficacy lasting roughly 20 minutes to, as you stated, OAV being effective for up to 3 days post treatment. 

Until we prove this variable for certain, I think we will only have anecdotal stories to tell of our personal experiences with OAV.

These anecdotes will vary from region to region. Our successes and failures depend on many more variables than just whether we are killing mites. We all have different brood loads, viruses loads and virulence levels of viruses. We cannot expect to have the same experiences when we are not suited the same.


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## Robert Holcombe (Oct 10, 2019)

OAV efficacy is based on scientific, peer reviewed test data. Unfortunately it is mostly northern climate based and originates from Europe and Eastern Europe. OAD effects are different from OAV - basically a faster effect and different path. OAV efficacy fall off with time in days and has a significant effect ( higher than natural Varroa drops) up to 10 days but it's is use full effective time period is 3-7 days for me due to high migration rates here. The end of the Fall foraging period, cold weather, falling brood counts and ROBBING creates a unique northern pattern - horizontally Varroa migration Varroa - copious amounts - 60 to 100 per day. OAV is very effective in that time period. I also find OAV far more effective as a test tool after removing supers to determine start of Varroa migration - with experience I can now simply see it happening and start treating. I would think the warm climate issue of continuous brooding raises the level of difficulty for treating. I know the Italians use the summer dearth to perform brood breaks as a routine. They also seem to prefer OAV and I did not hear of or read about any performance complaints. They also researched the effects of OA on honey for both OAV and OAD processes using isotopes.

The low temperature effects on OAV efficacy seem to be tied to data related to in-situ dead drop counts collected in eastern Europe. Apparently below 36F efficacy really drops off. No test description of thermal measurements nor hive design was provided - slightly above anecdotal? 

One of my backyard test plans will be an observation and data collection plan of an OAV treatment on an R10+ insulated hive in Jan., Feb, and March while monitoring temperature and relative humidity. 

"Forced brood breaks", I have determined, are not needed here as cold weather provides a natural brood break. My current final OAV treatment is a selected warm January afternoon around 38-40 F and sunny. Annecdotal statistic - 19 for 19 over two years but with Spring queen issues.


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## psm1212 (Feb 9, 2016)

Robert Holcombe said:


> OAV efficacy fall off with time in days and has a significant effect ( higher than natural Varroa drops) up to 10 days but it's is use full effective time period is 3-7 days for me due to high migration rates here.


Robert: Is this your own observation or are you citing a study or studies? Also, are we equating mite "fall off" with mite death? As you know, phoretic mites are most commonly wedged deeply under the tergites and sternites of the bee with their mouth parts buried into the fat bodies. The fact that dead mites may take 24 to 72 hours to become dislodged from that position and fall to a bottom board does not indicate that the OAV residue killed the mite on Day 5.

The real question to me is the efficacy of OAV residue in a hive post-application _against mites that emerge from cappings post application_. I am not certain that mite drop counts after Day 1 are necessarily the best measure of that efficacy.


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## grozzie2 (Jun 3, 2011)

Robert Holcombe said:


> Unfortunately it is mostly northern climate based and originates from Europe and Eastern Europe.


Except ofc the data set used to get approvals for Oxalic Acid in the USA, that came from Canada, not Europe...


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## grozzie2 (Jun 3, 2011)

psm1212 said:


> The real question to me is the efficacy of OAV residue in a hive post-application _against mites that emerge from cappings post application_. I am not certain that mite drop counts after Day 1 are necessarily the best measure of that efficacy.


I've listened to talks by Medhat Nasr on mite control, he would know some of the details on OAV efficacy, he's the one that did the lab and field work for the approvals in North America. If memory serves correctly, he suggested that the highest drop occurs between 24 and 72 hours after application. I'm sure if one digs the papers he produced during those studies can be found, they will be public somewhere, he was in the employ of the Alberta government when the trials were done.


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## johno (Dec 4, 2011)

Psm, I doubt that there will be many mites feeding on bees while there is brood available unless the hive is over run with mites. It is unlikely we will get any real interest by academia in OAV as there is no sponsor to feed the system so that they might reap the rewards. All we can try to do is kill as many phoretic mites as we can and keep on doing so with emerging mites by keeping treatment intervals as close as we can. At this time there has been no meaningfull research that claims bees are damaged by OAV so it is a matter of continuing the treatment until there is no further significant mite falls unless we can find a better mouse trap that will keep those crystals in the hive continuously. No matter what form of treatment you go for there will always be the problem of your location which could create the problem of mite imports and if your hives have sticky boards random OAV treatments can help to see if the mite loads have suddenly increased. There is no easy way to keep ahead of the mite problem as we can see by the fact that the average new beekeeper stays with the hobby for around 3 years.


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## psm1212 (Feb 9, 2016)

Clip from a 2018 article by Rusty Burlew. Not a scientific opinion, just a statement of uncertainty about post-application efficacy. Like Rusty, I don't know the answer either:

_"In the rest of this discussion, I’m assuming that there is little or no residual activity after an oxalic treatment. A publication by Dadant states “The hive returns to pre-treated levels [of oxalic acid] shortly after treatment. Within days of vaporization, the bees will remove the residual OA crystals from the hive.” *Is there enough oxalic acid in the hive during the removal stage to kill emerging mites? I don’t know.*"_


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## psm1212 (Feb 9, 2016)

I agree with you Johno. I was an early (and illegal) adopter of OAV and I still rely on it greatly in my treatment protocol. Randy Oliver said that we should all stop looking for a silver bullet for mite control and pick up some brass knuckles. Because it is a year-round brawl with mites requiring multiple applications, and in some cases, multiple modes of attack. That has certainly been my experience.


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## johno (Dec 4, 2011)

psm we have come a long way with OAV, a few years back remember the discussions that went on and on about the OA breaking down to FA and CO2 well I hope that is now dead and buried and if not I will again post the pic of where I vaporized onto my bare arm. Around 10 years ago there was still the theory that you could keep mites in check with screened bottom boards and the Dowda method of using confectioners sugar, still being taught in beginners courses today I believe. Maybe that is one of the reasons for the 3 year average.


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## AHudd (Mar 5, 2015)

Yep, in 2013 I was told by someone from the U of Ar. Ag. Ext. that screened bottom boards were going to solve the mite problem. So, I got some screened BBs and some of those, "Throw away your chemical, Beekeeping the way it used to be," bees. 
Full speed ahead.
Hell of a wreck.
Alex


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## grozzie2 (Jun 3, 2011)

johno said:


> psm we have come a long way with OAV, a few years back remember the discussions that went on and on about the OA breaking down to FA and CO2 well I hope that is now dead and buried and if not I will again post the pic of where I vaporized onto my bare arm.


If you heat OA up to the breakdown temperature it will break down, wether you say so or not, it will.


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## JWPalmer (May 1, 2017)

Grozzie, getting it to that point is the problem. Water can be heated to the point where it disassociates and becomes oxygen and hydrogen gases. But that requires tremendous pressures to allow the temperature to get that high. Pure boiling water at sea level will never exceed 212°F, no matter how hot the pan you pour it into is. Same goes for OA. You cannot cause it to exceed it's sublimation temperature if it is heated in an open or vented container. Seal it up and keep heating, sure. How hot do you want to go?


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## Robert Holcombe (Oct 10, 2019)

I do believe Canada depended heavily on European research and created their version of applications. I think they added the concept of no treating while supers are on due to lack of honey standards. Europe generally uses total acidity testing as part of their honey testing program. Lacking a requirement resulted in a banning the use of OA with supers-on. It is a somewhat next logical step or a pure marketing ploy - my opinion. My reasoning is OA has a half life shorter than formic acid 

As EPA approval was a 2015 event. I read mostly European test literature about OAV as US data was lacking ( no profit motive?). It has also been a while so this is dependent on an aging memory.


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## johno (Dec 4, 2011)

Can anybody show me where the formic acid is.


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## Robert Holcombe (Oct 10, 2019)

psm1212 - " Is this your own observation" - most, 95% or more, are based on some technical source. When I develop numbers I usually define the method. 

I have never seen an efficacy based on capped Varroa or emerging Varroa with bee emergence. In fact my memory tells me most efficacy test were done on brood-less or near broodless colonies or a specific sequence of steps to capture a clear mite population baseline. For OA I believe the treatments were conducted ( Univ of Sussex for in-situ examples) on broo-less or with brood colonies. Dead drop counts at specific time periods were collected including prior to treating Varroa drop counts. Post aperiod of time ( 10 or 20 days) the colonies would be treated with another proven chemical and counted providing a basis for efficacy calcualtions. I also think I read a test in which the colony was euthanized, bees collected ( and brood?), put through a special water washing procedure a nd filtering to verify efficacy.. OAD and OAV phoretic mite kill efficacy is firmly established for brood-less colonies and an implied equal efficacy for colonies with brood and phoretic mites. The range I remember is a low of about 86%, typical 93% and a high, double winter treatment of 99.7% .

I have never seen ( memory?) a test setup to identify the a time time based efficacy for emerging mite treatments. The closes approach to this issue, I recall was a preliminary Univ. of Hawaii test based on formic acid. I never could find the final or preliminary again. I may have saved it somewhere in Apple's incredible filing system. 

Fall-off is accounted for in exacting efficacy testing I have read. Do I use it? Likely as it is simply summed into count including live Varroa on the sticky board. What is missing is Varroa carried away by other creatures with access to the sticky board - accurate counts require any opening to be closed. It ants are running around the count will likely be low - my opinon. 

Test reports establish values based on certain boundary conditions. Field applications are up to the individual within certain EPA approved guidelines. Via my observations, since EPA approval, include natural, time based dead and live drop plus the effects of the treatment which is obvious. My method of accounting for or trying to kill emerging mites after treatment is to treat, especially in the Fall with horizontal spreading of mites, on a 4-5 day elapsed time schedule with a count on the 3 to 5th day (depending on predicted weather). Any total numbers above 100 treated treated again, 50-100 depends on hive size and judgement, below 50 in early Fall is a wait, more than 10 in Jan. gets another treatment. A treatment in Jan is typically brood-less sor near brood-less, a double treatment, 10 days(?) apart, in January in RI is reported by the Univ. of Sussex have an efficacy 99.7%. My observations for the past two years is I do not have to treat again until supers are off and robbing begins in the Fall. I do monitor capped drone brood for mites as the summer wears on. I have not seen DWV for two years. I grow my own bees, have open-mated queened hives and purchased mated queens. I now have no disease loses for two year ( observational) but do have queen issues (observational). 2019 - 2020 wintering result, 9 for 9 alive into Spring, two 1st year queen issues so far; drone layer and failed supercedure ( observational). 

Where did the feeding Varroa drop data, 24 to 72 hours, come from? To clarify, I do not count on day one but prefer 4-5 days post treatment and a quick visual scan at day 3. Also, I have seen no test report other than a quick petrie dish experiment proving the OA mechanism for killing a Varroa mite. I did read an Italian report using isotopes to time trace OA through a bees body. Does a faster dead drop when using OAD versus OAV imply a direct mite feeding kill? 

Let me know what you find in your search as my OAV application skills are still evolving. BTW, I wonder what the impact of my somewhat unique insulating style with no top vents, in winter, affects my winter OAV treatment.


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