# Potential for Miticide Resistance



## JSL (Sep 22, 2007)

snl said:


> Yes, but in Europe as here, not all the mites were killed in the treatment process and those mites not killed (after 20 years) _*STILL*_ have not bred mites that are resistant to OA.


Not wanting to hijack thread... This comment was interesting to me. My original comment was meant to point out that when a product comes to market and sees a high rate of use, it simply creates the potential for resistance to occur. 

Commercial beekeeping in the US and Canada is intense and our options for miticides are limited. The recent interest in Oxalic has created a bit of a frenzy. While Oxalic has seen a limited use in the past, it is coming to the forefront, which increases it's exposure to Varroa and intensifies any potential for development of resistance. This appears to be true of anything we have thrown at them previously.


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## grozzie2 (Jun 3, 2011)

I agree on the 'frenzy' we are seeing, just need to read some of the other sections of beesource to see how much of a frenzy it is. I have some thoughts on OA vaporization, totally unrelated to resistance, but I think by this time next year it's going to be getting a very bad rap from folks that are using it, not understanding it's capabilities and limitations, then being quite disappointed in the results they get. I think we will see less of that here in the commercial section of beesource, most of the folks reading here do understand those capabilities and limitations, and are trying to figure out how to work effectively within them.

The first, and most important thing to understand with OA vapor, it does NOT effect mites under cappings, and was originally presented as a treatment to be used when the bees are broodless. Most of the folks doing it right now are using OA vapor on hives that have brood, then in many cases counting mites a few days later. The piece they are missing is this. If you vaporize today, then count mites a week later, you are counting mites that emerged after the vapor effects die off. Then they will report 'I vaporized, and the counts still went up', and erroneously report that the OA vapor had no effect on the mites.

The second alarming thing is to see how many folks are using home-brew vaporizers, and I've read folks suggesting temperatures of 1200 degrees are required to 'get vapor flowing'. Overheat the OA, and it will have no effect on the mite population, but you will still see a cloud of 'vapour' coming from the gadget, it's just the wrong stuff.

I am expecting a lot of talk over the next 6 months about 'mites resistant to OA', when in fact, the real issue is that folks are improperly applying OA, and not understanding how to do it effectively.

In terms of discussion of potential resistance to OA developed in the mites, and anecdotal commentary online about ineffective treatments, it's going to be very difficult to separate the wheat from the chaff.


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## acbz (Sep 8, 2009)

Very well said.


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## TWall (May 19, 2010)

Joe,

My understanding of the mode of action of oxalic acid is that it tends to be more physical as opposed to a biological pathway. This makes development of resistance much more unlikely.

Sub-recommended applications will result in poor control but shouldn't result in increased resistance.

Tom


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## johno (Dec 4, 2011)

grozzie2, the fact that OA only effects phoretic mites is well understood by users of OAV, Hence the multiple treatments after honey is harvested. I am not so sure that the overheating of OA causes too much of a problem as OAV plus formic acid could be produced and mites don't like either. Also most OAV users will also treat when colonies are broodless. You might even take a look at the equipment and hardware section and you will find under home made vaporizers that temperature control of the vaporizer is practical and cheap.
Johno


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## enjambres (Jun 30, 2013)

I know this is the commercial side, and unlikely to be the case here. But I have been dismayed by the number of people who have clearly not understood the directions (and underlying rationale) for using OAV. People who are "treating" with a single dose in hives with brood and then are perplexed when they get poor results. People who think they should treat once a month, etc. And similarly, people who think an extended series of OAD (in the absence of OAV equipment) will work as well, and as safely, as an OAV series.

I am not completely reassured about the issues around under-dosed or ineffectively-treated mites and OAV. I think that we will begin to select for more resistant to OAV mites. Hopefully not for quite awhile, but I think it will happen. It's the same fundamental process that people pin their hopes on for developing mite-resistant bees: evolutionary selection. It's baked in.

Enj.


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## JSL (Sep 22, 2007)

I agree acbz, I think grozzie2 said a mouth full.


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## JSL (Sep 22, 2007)

TWall said:


> Joe,
> 
> My understanding of the mode of action of oxalic acid is that it tends to be more physical as opposed to a biological pathway. This makes development of resistance much more unlikely.
> 
> ...


Tom, I have thought that too and agree with you, but also think there are some amazing examples of “resistance” mechanisms out there. It seems that were there is a will there is a way…
I tend to think of Bt resistance that way, or when I was in grad school, a friend described a interesting example of DDT resistance to us. He was from South Africa and as it turns out, it was not resistance to DDT at all, but rather the application method. They would spray the inside walls with DDT, because after a blood meal, the mosquitoes would land on the walls for a rest. They soon selected for “dine and dash” mosquitoes, those that would fly way after a blood meal. Simple yet effective.


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## johno (Dec 4, 2011)

I guess we all know that the solution to the mite problem is to have resistant bees, now after saying that can anyone point me in the direction of a supplier who can supply such bees. I am not talking about all the queens that are called mite resistant and their colonies die any way if untreated, so until that time comes we have to keep our bees alive any way we can and OA and formic are the cheapest and are doing a great job so until they fail I will continue to use them. That does not mean that I refrain from adding VSH or grooming genetics to my colonies every year but I doubt that I will see treatment free bees throughout the USA in my lifetime.
Johno


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## JSL (Sep 22, 2007)

There are many aspects to the development of resistance. Time is commonly cited as an umbrella factor, but within that, which I think is more important is usage and coverage. Oxalic has been a low usage product, not many chance encounters in all these years with “potentially” resistant individuals, by whatever mechanism possible. Fast forward into heavy usage and you increase the opportunity to encounter those special mites, IF, they even exist. It is a chemical exposure, so there may be some novel pathway for them to utilize.


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## acbz (Sep 8, 2009)

JSL said:


> I agree acbz, I think grozzie2 said a mouth full.


My understanding is that fluvalinate and coumaphos acted on specific sodium channels in the mite nervous system that random genetic mutation could quickly overcome. Amitraz appears to be a bit more general in mode of action and thus its continued effectiveness. I'm not sure if OA mode of action is understood yet, but appears to be "physical" as previously stated. Realizing that I am by no means a biology expert, I'm looking for your take on this, Mr Latshaw. Randy O seems pretty sure that OA resistance is possible. Can your shed some light? 
Aaron


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## ApricotApiaries (Sep 21, 2014)

JSL said:


> Tom, I have thought that too and agree with you, but also think there are some amazing examples of “resistance” mechanisms out there. It seems that were there is a will there is a way…
> I tend to think of Bt resistance that way, or when I was in grad school, a friend described a interesting example of DDT resistance to us. He was from South Africa and as it turns out, it was not resistance to DDT at all, but rather the application method. They would spray the inside walls with DDT, because after a blood meal, the mosquitoes would land on the walls for a rest. They soon selected for “dine and dash” mosquitoes, those that would fly way after a blood meal. Simple yet effective.


You nailed it. Behavior like everything else can be selected for. And applications of oxalis acid is a selection pressure on the mites. I can think of several mechanisms of resistance thatcoyldpotentislly be selected for. These include but are not limited to...
Less phoretic time, better hiding during phoretic time, thicker carapace...
Any behavior that reduces the chance of exposure to italic acid has the potential to lead to resistance, any morphological change resulting in reduced efficacy has the potential to lead to resistance.


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## JSL (Sep 22, 2007)

acbz said:


> My understanding is that fluvalinate and coumaphos acted on specific sodium channels in the mite nervous system that random genetic mutation could quickly overcome. Amitraz appears to be a bit more general in mode of action and thus its continued effectiveness. I'm not sure if OA mode of action is understood yet, but appears to be "physical" as previously stated. Realizing that I am by no means a biology expert, I'm looking for your take on this, Mr Latshaw. Randy O seems pretty sure that OA resistance is possible. Can your shed some light?
> Aaron


In the interest of full disclosure, this is not my area of study, but still very interesting. I know there are more experienced beekeepers out there that could add to this.

Aaron, I think of Bt as an interesting and slightly complex example because it has been widely studied. Bt is a crystalline protein. In a crude sense these naturally occurring proteins have been incorporated into plants that are ingested by pests and then the crystals then punch holes in the digestive systems of the pest, giving them a pretty severe belly ache, allowing bacteria and other things to take over. There have been some pretty ingenious ways that insects have overcome this toxin. Some simply modify the binding sites inside the guts so the crystals are not as damaging. Some have an increased ability to breakdown the toxins. Some have an increased ability to replace/repair their guts. It is interesting that some species have developed multiple ways of dealing with Bt. Some species are fortunate to have such tools lying around in their “tool box” and develop resistance more quickly, while others simply don’t have the inherent ability or must develop a more complicated work around. The take home for me is that we are seldom so fortunate to completely outsmart “Mother Nature”.


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## Ian (Jan 16, 2003)

why all the fuss over the frenzy Joe?


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## JSL (Sep 22, 2007)

Ian said:


> why all the fuss over the frenzy Joe?


Ian,
I have a couple of reasons. First, I think when beekeepers latch on to something like this there can be some real disappointing, if not disastrous outcomes. Some, not all, may jump in without testing and think they are good. Then there is the other end. If and when it is no longer effective the tail end can be equally as devastating. Some may become complacent and skip post treatment checks and find that year when it really didn't work and it is too late.

I also think beekeepers share an equal responsibility in using miticides. We want whatever is giving the highest control rate and use it all up. Can we be content with less efficacy and prolong the product lifespans? I realize this smells of altruism, but with a little effort, we might help ourselves.

Last, I sure hope everyone that will drop the money on a vaporizer will also purchase the proper safety gear. Unfortunately, I am afraid many will not and chemical burns can be pretty nasty.


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## jean-marc (Jan 13, 2005)

Anybody who does not purchase the proper safety gear will likely be running to the nearest Lowe's store after 30 seconds of fumigation. Remember organic vapors/acid gas cartridges. I can see guys buying the wrong cartridges, definitely do not try to go without. You might do it once, never a second time. It is just way to harsh on the body.

Jean-Marc


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## Ian (Jan 16, 2003)

OA has been registered in Canada for sometime now. It's the commercial application our fall broodless conditions which has drawn our attention


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## Ian (Jan 16, 2003)

And yes be sure it's the organic vapour and acid gas filters


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## JSL (Sep 22, 2007)

Ian said:


> OA has been registered in Canada for sometime now. It's the commercial application our fall broodless conditions which has drawn our attention


Yes, I am aware. Six or seven years ago, Medhat invited me up to do some queen rearing courses with him and I had the opportunity to see some of the earlier prototypes, but they did not receive the attention they are today.

I used OAD probably 9 years ago and still use it to knock mites off of packages for sampling. Both forms work well, but it is all about timing.


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## Ian (Jan 16, 2003)

Ya the drizzle works well, but wrong timing and hard winters ... 
The appeal with the new improved vaporizers is the ease of treatment on bees , and follow up Applications. Have you used those older vap devices..?? Lol

If I can at least glean some advantage from this winter, I'm interested


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## JSL (Sep 22, 2007)

Below is a PM that was sent to me. I am posting it with permission, but will let the the person chime in and claim it if they wish. A point that was impressed upon me as a kid was that many advances in a given field come from the outside made by individuals with a completely novel perspective... 

Pesticides that have to be transported a long distance inside the target organism often result in fast resistance development. This is simply because such long transport offers the organism lots of chances to degrade the stuff before it gets to the site of action. Take neonics as an example. Literally millions of neonic molecules per neuron in the insect's brain must enter an insect to kill that insect. Another factor can be what metabolic pathways the insect already has before first exposure. Flies had a pathway to degrade carbon chlorine bonds before they were ever exposed to DDT. Mosquitoes did not have such a metabolic pathway. The net result was Flies developed extreme resistance to DDT within a few years while mosquitoes never developed resistance to this day even in areas where DDT has been used continuously for 70 years.

There is a preventative fungicide (Chlorothalonil) that has been commercial since 1970 which has never had any fungus develop resistance. This material acts by dissolving in the dew on plant leaves and killing the hyphae on newly emerging fungi spores. On a cellular level this chemical is really toxic. However, it has miserable transport properties and does not penetrate the wax surface on leaves or get absorbed by your gut if you swallow it. By contrast there are several systemic fungicides that are curatives and act within the plant to stop fungi that are already established. Resistance development in such cases is generally rapid.

We really do not know how oxalic acid acts. It seems a decent bet it acts externally somehow. If this is the case resistance can develop if the external surface can be modified to be less acid sensitive while still functioning normally. I am sure the surface can by modified to be less acid sensitive. I am not so sure the modification can provide normal functioning based on field observations in Europe where no resistance has been reported to date.

There was a very nice paper in Science in June of this year on the optimum kill to postpone resistance development. The subject is very complicated. You need to know the rates of various pathways for both toxic action and metabolism and at the end get a differential equation to solve. But, to make a long story short getting a very high kill is occasionally the best way to slow resistance development, but other times you only want a 2/3s kill rate. The idea that a very high kill rate slows resistance development simply is not always true. In fact it has been well known now for at least 40 years that it was not even generally true. Remember, even in antibiotic treatments for many antibiotics the dose of chemical is not sufficient to kill the problem bacteria. It just stops the bacteria from reproducing and gives your immune system time to mop up.


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## Ian (Jan 16, 2003)

"Mop up" is what this OA treatment is intended to do in my operation. End of year clean up. 
Last few years after I've started to manage exclusively in singles I've been able to hold my mite load with an annual Apivar treatment. Just before we bring them in for winter the hives are broodless, a point in time the mites are at their most vulnerable state fully exposed. This OA apparently sickens the mite, less so with the bees, at a time the mite needs to hang on for a few months. 
As theory states, changing up treatments prolong the efficacy of them all. 
Time will tell how long efficacy will last, 

Until then, capitalize
Theory's on the possible problems in regards to resistance is only important when it actually happens. As with everything else in this business getting to next year is the challenge


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## TWall (May 19, 2010)

Joe,

My memory for the details is getting a little foggy with time. But, it is interesting I learned the most about developing resistance to pesticides in a biological control of insects class. There was extensive discussion about the need for biological control using DDT resistance as a case study. Improper treatment is a leading cause of development of resistance. While we like to see high control/kill levels it often results in quicker resistance by only leaving resistant individuals to breed.

If varroa were to develop resistance to OA I would expect if to happen fairly quickly since it is now used so widely. I assume that it is applied with varying compliance to application guidelines which could hasten resistance.

The DDT resistance you mentioned was interesting. The mosquitoes didn't become resistant to DDT but to the application/treatment method. The population shift occurred because only the mosquitoes that flew outside avoided the DDT. It reminds me of the story of white moths in London. When coal usage dropped there was less soot in the air so white moths stayed white instead of turning gray. This made the moths more visible to predators.

This may be false thinking on my part but, I kind of think of OA like bleach. There are microbes that have developed resistance to bleach. But, most have not because of the way it works physically. I guess it boils down to physical versus biological modes of action. I am not sure motes can develop a thick enough cuticle to avoid being injured by OA, assuming OA works physically. I guess that is the $64,000 question, what is the mode of action of OA?

Tom


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## Fusion_power (Jan 14, 2005)

> It reminds me of the story of white moths in London. When coal usage dropped there was less soot in the air so white moths stayed white instead of turning gray. This made the moths more visible to predators.


 During the industrial revolution, normal gray moths were disadvantaged because so much soot was in the air that trees turned black making gray moths stick out. Melanistic (black) moths were a natural but very low percentage of the population. Over the years, the black moths survived because they could not be seen and eventually became the bulk of the population. Fast forward to the end of the coal burning era and the air was cleaner which meant the trees were no longer black. This made the melanistic moths more visible, therefore the gray moths rebounded and became the dominant group.


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## JSL (Sep 22, 2007)

Ian said:


> Until then, capitalize
> Theory's on the possible problems in regards to resistance is only important when it actually happens. As with everything else in this business getting to next year is the challenge


I understand this from a purely business perspective, but I feel like the old curmudgeon in the room from a good stewardship approach.


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## jean-marc (Jan 13, 2005)

As with everything else in this business getting to next year is the challenge[/QUOTE]

This is the simple truth of this business. Anything else is a distraction. At the end of the day no matter what, we all have to/want to get to next year, even if that means burning some of those long term bridges. It has become difficult to sell honey at a good/fair price to the producer so getting to next year has become even tougher. Any and pretty much all of the challenges can be overcome if the right amount of cash comes into the business. I am not about to loose sleep over possible OA resistance of the mites. It is futile. If it comes, it comes, if it does not, it does not, simple. There are no indications that this will happen. Until then we have other more pressing issues.

Jean-Marc


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## Ian (Jan 16, 2003)

JSL said:


> I understand this from a purely business perspective, but I feel like the old curmudgeon in the room from a good stewardship approach.


Oh the old curmudgeon brings the countering position which drums up conversation. :thumbsup:

This targeted OA treatment approach IS from a position of good stewardship. How can you see it any other way?


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## Ian (Jan 16, 2003)

I waste my time on social media from time to time. I'm part of s few beekeepering groups like this one of Beesource. 
The amount of ignorance and the lead to TF beekeeping is staggering, practicing TF merely on the stand point that it's TF...and as predicted the group's are now plugged full with stories of complete hive crashes...and blame on farmers. 

I view what I'm doing as good Stewardship, disease control is good stewardship


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## JRG13 (May 11, 2012)

What you mean Ian... it's always some spraying, gmo's, or neonics that kill the once healthy hives in late fall..... 'I never saw any mites' so it wasn't them.


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## Vance G (Jan 6, 2011)

When notables such as Mr Latshaw and Mr. Oliver both have cautions about breeding mites that can defeat Oxalic acid crystals, I think it is worth worrying about and considering how to rotate treatments to forestall that resistence. I had a commercial beek tell me this summer that the secret to killing mites for him was a low intensity presence of amitraz in his hives as much of the year as possible. That is when I knew that my use of the wonder strips was ending.


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## JSL (Sep 22, 2007)

jean-marc said:


> As with everything else in this business getting to next year is the challenge


This is the simple truth of this business. Anything else is a distraction. At the end of the day no matter what, we all have to/want to get to next year, even if that means burning some of those long term bridges. It has become difficult to sell honey at a good/fair price to the producer so getting to next year has become even tougher. Any and pretty much all of the challenges can be overcome if the right amount of cash comes into the business. I am not about to loose sleep over possible OA resistance of the mites. It is futile. If it comes, it comes, if it does not, it does not, simple. There are no indications that this will happen. Until then we have other more pressing issues.

Jean-Marc[/QUOTE]

I am not losing sleep over the idea. I just like to be prepared. It is nice to have an ace or two in the back pocket. It is rather enjoyable to think through different scenarios and see which one’s actually play out. I think Keith has a nice little saying about this topic, that ends with those standing there wondering what just happened. 
Running a business on short term objectives sounds more stressful to me.


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## JSL (Sep 22, 2007)

Ian said:


> I waste my time on social media from time to time. I'm part of s few beekeepering groups like this one of Beesource.
> The amount of ignorance and the lead to TF beekeeping is staggering, practicing TF merely on the stand point that it's TF...and as predicted the group's are now plugged full with stories of complete hive crashes...and blame on farmers.
> 
> 
> I view what I'm doing as good Stewardship, disease control is good stewardship


What are people thinking? How could anyone run a successful treatment free operation? 
I hope it does not come across as though I am advocating treatment free commercial beekeeping. Those who know me, know I have a little more forethought than that. Just too many pressures.
Your colonies look nice. Your efforts show. However, I think stewardship extends beyond your own farm gate.


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## Ian (Jan 16, 2003)

Stewardship does not extend past bankruptcy either. Using OA to kill mites leans towards improving the stewardship of the farm in everyway. It's another tool in part of proper rotation


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## jean-marc (Jan 13, 2005)

It is nice to have an ace or two in the back pocket. [/QUOTE]

Sure, we all like to have them. Trouble is the regulators approve 1 treatment at a time, wait until the efficacy is too low to provide any usefullness, then approve another product once beekeepers start hurting. Easy to blame beekeepers, but I think that responsibility lies with the regulators. Apparently Canada is working to approve Bayvarol. The active ingredient is a close cousin to the active component in the Apistan strips. If you have varroa that are resistant to fluvalinate it will not be long before they are resistant to flumethrin, the active component in Bayvarol strips. It is easy to rotate chemicals if you have access to them.

Jean-Marc


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