# OA Questtion



## sc-bee (May 10, 2005)

Hi Janet,
I have had a lot of questions myself about OA. Seems it can be evaporated or dribbled in. Seems for the hobbyist evaporated in seems to be the method of choice. A lot of debate and concern about the safety wearing respirators etc.
I understand if you dribble you can only do one treatment (when the hive is broodless of course) because it is so hard on the bees. I have not tried it only investigating. Check out beewranglers site and do a search on OA. Read a lengthy post a while back about the two methods and their use--seems dribbling has been used in europe for some time but the consensus seems to be they are moving to vapor instead.
I would search and post a couple for you but my accelerator is down on my dial-up and it would take eons  .
And thanks for your continued post on the powder treatments.


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## 2rubes (Apr 28, 2005)

Thanks for your reply. I looked at Dennis' site and couldn't find why it works. I did start a search and mostly am finding post on how much to use and techniques. Just how does it kill the mites? Beekeepers at our club, who used it as their first treatment talked about huge drops of mites, their sticky boards were black. They hadn't tried powdered sugar or just did one treatment last year. Really, you do need those multi-treatments to take care of an infestation.
I just can't stop thinking about OA and how it might work. We've used the flea-product, Advantage, and we could hardly pet our dog. I take vit-b for fleas and mosquitos and I never get bite anymore. So, are people dribbling in OA and the bees injesting it, and then turning it into nectar that they eat later? When you feed bees sugarwater, they turn it into nectar for food, that's the idea. Powdered sugar can have cornstarch. OA solution has chemicals that are found in honey. Maybe like we use vinegar. Honey and vinegar, that sounds like salad dressing, maybe it is good (grin).
We haven't used sugar water in a few years, with an exception this spring when the weather was so weird out here, hot, cold, hot, cold and suddenly no stores. We just did it for a few days to give them a boost. And now with the powdered sugar, I know they are converting them into store stores in the fall.
I mostly care about keeping our bees alive, and will do what it takes. I just can't leave them to 'survive.' Sort of like our kids and animals. We innoculate them and if we have to, we give them drugs to keep them alive and get them healthy again so they can do it on their own. I did used Apistan way back when, and was so happy when we got it down to once a year.
So, does anyone know exactly how dribble OA kills mites?? Was my friend right?
Thanks,
Janet


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## Dave W (Aug 3, 2002)

Mode of Action - When consumed (solution [DLW,12/05]) by bees, probably acts as a protoplasmic poison by acidifying host bees hemolymph [ABJ, 6/04, p479]. 
 Mode of action appears to be low pH of OA solution [Ref 116].


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## drobbins (Jun 1, 2005)

Janet,

there have been several discussion here on the mode of action
it's clear nobody really understands it
even DaveW's reference qualifies there statement with "probably"
I've used the vapor
the most common thing I hear is that the acid damages the mites delicate mouth parts and cause it to starve
however, I don't think anybody can prove this and I must say that the speed with which it kills the mites would suggest they aren't waiting around to die
there is also a school of thought that the acid damages the mites chitin outer body covering and this cause them to lose moisture and dessicate
that actually sounds a little more plausible to me considering how fast it works but I'm just speculating
I think the bottom line is nobody knows how, it just works
(comforting when you put it an foodstuffs, no??)
I will mention that considerable testing has been done to determine OA residue in honey and wax and there is none, zero
I've seen studies that back that up, if I can dig up a link I will post it

[edit] oh yea, I would mention the problem I see with OA
it doesn't kill the mites in the cells so if you have a problem mid summer it's not such a good solution
I would suggest it's a wonderfull complement to the sugar treatments you use
sugar keeps em down all summer
OA gives em the knockout punch in late fall

Dave

[ August 15, 2006, 11:42 AM: Message edited by: drobbins ]


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## Dan Williamson (Apr 6, 2004)

Janet,

I don't know how it works or what it does to the mites but I do usually get a pretty good drop after I treat. 

I have treated 2 years in a row. I have only treated in early and late winter. 

This past season I treated once in January and again 1 month later in Feb. In my area there is at best very minimal to no brood rearing especially in January. I had a fairly decent drop in January and a very minimal drop in Feb. 

I have not used the drizzle method to apply OA. I have used the vaporizing method. It is simple and cheap relative to other treatments. I'm not entirely convince that it would be quick and easy with a large # of colonies. I would estimate that it takes me approx 5 min per hive to treat. That includes prep time. Taping off any cracks etc... 

I am going to try apiguard on a couple of colonies and see how it works.

I really like OA. It has worked very well for me.


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## 2rubes (Apr 28, 2005)

You guys are awesome, thanks so much for the quick replys. I have a much better understanding now. 
Thanks again,
Janet


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## Dick Allen (Sep 4, 2004)

I think it works in the manner Dave W. posted, but Ill qualify that too as the other Dave (drobbins) points out. When OA is applied to the cluster by syringe it seems unlikely most of the bees will be wetted by the OA laced syrup. To me it seems more likely bees will be ingesting the syrup as they clean those that are drenched and then feed each other. 

I suppose there are vapors released into the hive from the syrup, but bees will be breathing them as they do when OA is sublimated by heating the crystals. Either by syrup or vapor I think the effects of OA end up in the bees hemolymph and poison mites that way. It's nasty stuff to breath. As I remember beekeepers have been cautioned a number of times on these forums about breathing in vapors of OA which was reported to cause kidney damage.

Most people seem to be of the opinion that OA damages mites by burning them. If you spend some time searching oxalic acid and bees on google you will find sites that prove OA kills mites that way, but there are some sites that prove OA acts as a poison through the bees blood. 

(Janet: thanks for posting your notes from the W.A.S. conference.







)


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## Michael Bush (Aug 2, 2002)

I don't think anyone knows for sure.







It's all theory. But it works.


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## Kieck (Dec 2, 2005)

I can't answer questions about OA -- I've never used it, and none of the other beekeepers that I know well around here have used it either. Some beekeepers on this forum swear by it.

Having said that, I read something in this thread that I've never read before, and it surprized me:

"Mode of Action - When consumed (solution [DLW,12/05]) by bees, probably acts as a protoplasmic poison by acidifying host bees hemolymph [ABJ, 6/04, p479]." -posted by Dave W

Something seems wrong about that idea to me. In most animals, changing the pH of blood or hemolymph will kill the organisms themselves. Even small changes in pH of these fluids are very, very dangerous. Could bees really survive having their hemolymph become more acidic? How would such a process work? For comparison, if I eat extremely acidic food, by blood does not become more acidic. If I work with strong acids, my blood does not become more acidic. Why would it be different with honey bees?


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## Dan Williamson (Apr 6, 2004)

I'm certainly not scientific enough to know about blood profiles and whether or not it kills mites by changing the blood chemistry.

I do know that when I have used OA you get a fairly quick response. Within 24hrs you will have a fairly large mite drop. 

In fact within 30min I have seen numerous mites on the sticky board after vaporizing and they were already dead.

My unscientific, amateur, unstudied, observation is that the OA does something to the mite itself.
What that is I have no idea.

At least on the surface, the bees do not seem to be the least bit affected. 

I had a fairly high level of queen supercedure when fogging with FGMO. I have not lost a queen to vaporizing OA nor seen supercedure issues.


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## Dick Allen (Sep 4, 2004)

Copper gluconate is reported to change the blood make-up of bees enough that mites die when taking in bee blood. Now, granted there hasn't been a huge amount of research on the subject and further some people who've tried it haven't had spectatuclar results, but the one study many people cite does say mites are killed by poisioning after ingesting bee blood.


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## Kieck (Dec 2, 2005)

"Copper gluconate is reported to change the blood make-up of bees enough that mites die when taking in bee blood." -Dick Allen

OK, but I believe that's adding a chemical to the hemolymph of bees, not changing the pH of their hemolymph. I assume copper gluconate could somehow be absorbed into the hemolymph at sub-lethal levels to the bees. 

I think of the copper gluconate more like treating mammals with Ivermectin, or putting Frontline on dogs. The chemicals are present in the animals, may not be entirely healthy for the animals, but the risks associated with the chemicals are less than the risks associated with the pests that might otherwise attack the animals. Those chemicals do not significantly change the pH of the animals' blood, though.

As far as the "mode of action" of oxalic acid, I would venture that it simply "burns" the mites. It might damage their mouthparts, too, but why worry about the mouthparts if the mites are already dead? Splash a strong acid liberally over your body, and you'll likely die, too. The amount of the OA must be enough that it doesn't kill the bees (maybe for the bees it's similar to humans getting burns, but not severe enough burns to kill them).


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## 2rubes (Apr 28, 2005)

Ive been pondering all of this information. Thanks Dick, I forgot to mention, Randy Oliver was there, and he read and corrected my notes. As you saw, there were great speakers. I want to mention Jim Bachs talk about formic acid. He talked a good deal on all of the safety equipment, respirators that were fitted, special gloves, it was down right scary. 25% queen loss, damaging to brood, irritates the bees into grooming, dont use on weak colonies, etc. I' sure he's involved with the product. 
Randy Oliver questioned Diana Sammataro on damage to brood with her OA experiments, but they were not looking for that. 
As I mentioned, a lot of people in our clubs are using or are planning to use OA as a final knockdown, after a year of bringing their bees back using powdered sugar. I can see that becoming more the norm. And they are using the dribble method, mostly because Randy advocates that, and mostly because of the safety factor. A few of the larger commercial guys are using OA vapor.	
A few people in our group have said sugar really upsets the bees, and OA doesnt seem to bother them. Randy actually says they look peppy afterward using OA. Maybe the powdered sugar doesnt slow them down, and OA is toxic for a while, just to the point that its a seditive and then it wears off. Who knows? That its hard on the bees, can burn our skin and you need to wait for the honey supers to come off leaves me sort of uncomfortable. I would make that my second choice, when the first choice wasnt working.
I can see using OA dribble right now, going into winter, as way to save your bees. You would have to be so intensive with powdered sugar, maybe doing it every 4 days or so for a few weeks, then once a week for a few more. I can see that would be a lot of work. I know, I did it all last year. This year has been a breeze. I had a higher count in one hive that got a lot of shade. We took it apart, put frozen frames of drone brood in and decided not to powder sugar, since we will be removing the supers next week and will PS all of them.
Right now our counts are so low, were going to continue on with doing one more powdered sugar treatment, 3 times this august and once late fall/early winter and well check counts every so often.
Yesterday, Mike and I watched brood, saw two bee emerge, no mites, Mike got bored. Lots of bees, eggs and lots of brood, no chewed wings. Didnt see drone cells anywhere. And they are putting in pollen and honey under the brood nest, ala Walt Wright.
This has been a great post, thanks for all of your views. 
Sincerely,
Janet


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## Dick Allen (Sep 4, 2004)

I certainly don't mean to turn this into a "debate", but I'm still uncomfortable over OA burning mites. The usual method of applying as a syrup is to use a syring and drizzle it over the bees along the top bars. OK, I can accept mites being burned that way, if indeed they are. But, the question I have not had answered is what about all those bees in the cluster. I still doubt they are going to come into direct contact with the syrup. Some mites could, I suppose, if they are on bees that groom the wetted bees, but it certainly seems to me that bees in the center and lower part of the cluster are simply not going to come into direct contact with the syrup. As Canadian beekeeper Allen Dick (not to be confused with U.S. beekeeper Dick Allen  ) sometimes says "Enquiring minds want to know" 

Edit: Wouldn't you know it, After pawing through piles of old ABJ's I couldn't locate the June '04 issue. 

[ August 18, 2006, 11:59 AM: Message edited by: Dick Allen ]


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## Kieck (Dec 2, 2005)

"But, the question I have not had answered is what about all those bees in the cluster." -Dick Allen

I don't understand this part, but maybe that's because I've never used an acid as a treatment. When I open my hives, my bees are not clustered. They're all over the place. Only in cold weather do I see a cluster starting to form.

Regardless, though, (and I'm not trying to start a debate, either) oxalic acid must be a contact poison. Otherwise, why wouldn't it kill the mites in sealed brood?

If the mode of action is the low pH of the solution (" Mode of action appears to be low pH of OA solution [Ref 116]." -Dave W), then it sounds like "burning" to me. Call it "burning" or call it "caustic," it's about the same.


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## Dick Allen (Sep 4, 2004)

In cold weather when the cluster forms and is broodless is the generally recommended time for treating with oxalic acid. So, do all the bees in the cluster come in contact with oxalic acid laced syrup? That's the question I'm after. Maybe they do, but it seems to me they wouldn't. As far as it not killing mites in sealed brood, well how could it? If it does work as a systemic as I'm inclined to think it might, then mites will still have to ingest it won't they? They certainly can't do that if sealed in brood. Copper gluconate likely won't kill mites in sealed brood either, will it? My understanding is that when it does kills phoretic mites, it does so after they have consumed bee hemolymph. 

This is the rest of what Dave W. wrote:
"probably acts as a protoplasmic poison by acidifying host bees hemolymph" 

I wish I could find that ABJ issue.


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## manbee (Sep 22, 2003)

when using OA in vapor form what type of resparator 
should be worn and how long should the vapor be in the hive? I understand that OA in vapor form works best at the end of the brood rearing seacon.


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## Mike Gillmore (Feb 25, 2006)

This msds will give you the type of safety equipment needed when using OA vapor. I take the precautions seriouly, but I just bring my smoker with me and watch the direction of the wind... and stay upwind with a 12 foot jumper cable attached to the vaporizer.
http://www.iri-us.com/msds/oxalic.html


These two sites are companies that make vaporizers and they give you general how-to instructions for their vaporizers
http://www.dave-cushman.net/bee/oxalicthorne.html

http://www.members.shaw.ca/orioleln/Oxalic_Acid.htm


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## 2rubes (Apr 28, 2005)

I sent this post off to Randy Oliver, our mentor and he wrote back and asked me to put this on the post. 

"No one knows the mode of action of oxalic acid. Earlier European literature assumed that it changed the pH of the bees' haemolymph, and since varroa uses the proteins in the bee haemolymph without digestion, it was assumed the the pH killed the varroa directly. Anyone can note, though, that the bees don't eat the syrup on the top bars, and likely not that on their bodies. Work last year by Nick Aliano put that theory to rest, when he demonstrated in colonies split by various screens that the passing of honey sack contents by trophyllaxis did not result in varroa death in the non-oxalic'd hive half. However, physical contact by the bees did result in varroa kill. Oxalic seems to act as a contact "poison" (note the quotation marks). Oxalic acid dribble requires sugar to be added. Oxalic and water alone don't work. The sugar apparently acts as a glue, or possibly a humectant.

Based upon two observed phenomena, it is likely that oxalic works as a physical abrasive due to it's crystal structure, similar to the action of boric acid on ants, or diatomaceous earth on many insects:
1. Oxalic vaporization kills mites, and presumably the bees don't ingest it. It is likely that the vaporized acid forms tiny crystals when it recondenses on the combs. (There is also the possibility that some of the OA decomposes by heat into formic acid).
2. The plant Dieffenbachia is called "dumbcane" because it is full of oxalic acid crystals that puncture a human's tongue and cause it to swell up--causing the inability to speak.
Tell you what: I'll go evaporate some oxalic syrup on a glass slide now and check it under the 'scope and let you know if I see crystals.
This hypothesis could prove to be untrue, but it's the most likely one going at the present date.

I've done considerable work with oxalic, with great success, and will be publishing a series on integrated pest management for varroa in ABJ very soon, which will include a great deal of application safety and practical tips with oxalic. I also am experimenting with powdered sugar this week, because I believe I see a better timing method to apply it than the 3x once a week Dowda method. I also started today trials with thymol in several carriers. I'm also sending Jerry Hayes a correction today of an error he published re application of Tylsin. You'll also see a lengthy article by me in the Oct ABJ on almond pollination." Randy Oliver


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## Dick Allen (Sep 4, 2004)

Thanks Janet, I'm looking forward to reading Randy's series in ABJ. OA crystals causing physical abrasion is another interesting hypothesis. 

I received a copy of the June 2004 ABJ article Dave W. mentioned authored by Mike Stanghellini. In it he and Paul Raybold (NJ state apiarist) compare Apilife VAR, formic acid (MiteGone), oxalic acid, Sucrocide, and Apistan.


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## Doug R (Jul 18, 2001)

The limited reports that I've read indicate that OA levels do not increase in the honey or wax after vaporization treatment. Can anyone confirm this? If so, why is it recommended to remove the honey supers? Is it "just in case"?

Thank you,

Doug Rolley


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## drobbins (Jun 1, 2005)

Doug

I can't find the link but you're correct, there are scientific studies around that show no residue

as for supers, two reasons
1) you want to crowd the bees into the broodnest because it's smaller so it's easier to treat them
(the vapor get's diluted less)
2) just on general principal you never treat with anything while supers are on, not even powdered sugar. you're striving for the purest product possible

Dave

[edit]http://www.edpsciences-usa.org/articles/apido/abs/2002/04/Bogdanov/Bogdanov.html

[ September 05, 2006, 03:42 PM: Message edited by: drobbins ]


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## George Fergusson (May 19, 2005)

Well I can't imagine that you won't have some oxalic acid residue in a hive after vaporizing it. The vapor condenses readily, so where's it gonna go but onto the hive body walls, the frames and comb, and the bees? I recall reading a study about this somewhere.. I think it was linked into Bwrangler's site somehow. I'll see if I can find it.

[Edit] Well, finding Bwranger's web site was half the battle







I can't figure out how to cut and past a url with this here mouse-button derprived Mac I'm using, so here's the site:

http://www.mellifera.de/

Click on the "English" link in the frame on the left, bottom. There's 2 studies on the resulting page, one the efficacy of OA vapor treatments (very good!) and the other "Vaporisation of oxalic acid and working safety", an 80kb PDF file that goes into OA residues. I've read both studies several times.

[ September 05, 2006, 03:54 PM: Message edited by: George Fergusson ]


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## drobbins (Jun 1, 2005)

google turns up plenty of stuff
actually in the link I posted above they treated in fall and found no residue the next spring
in another I found they trickled in spring just before supering and found a small increase

http://www.beekeeping.com/articles/us/spring_treatment_oxalic_acid.htm

this is what drew me to OA (plus it kills lots of mites)

google "oxalic acid residue in honey"

Dave


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## xC0000005 (Nov 17, 2004)

I read the mds sheet here - is that type of respirator commonly available? I'd prefer not to kill myself while offing the mites with vaporized oa.


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## Michael Bush (Aug 2, 2002)

Stand up wind. Light a smoker so you can be SURE of standing up wind.


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## 2rubes (Apr 28, 2005)

Hi, I'm not sure how to link Bee-L to here. Randy Oliver wrote a piece on OA on Bee-L titled 'Oxalic Acid' here and he's soon to be published in ABJ both with an OA article and a 3part on Almond Pollination. Could someone help me on the link?
Janet


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## Dick Allen (Sep 4, 2004)

Well Janet, I hesitate to post this since he does not agree with my earlier belief that OA acted as a systemic poison.  

This will take you to September 2006, week 1 in the archives:

http://listserv.albany.edu:8080/cgi-bin/wa?A1=ind0609a&L=bee-l

To get to Randy's piece scroll down to:

"6. oxalic acid"


This can be bookmarked to take you to the Bee-L archives in general:

http://listserv.albany.edu:8080/archives/bee-l.html


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## 2rubes (Apr 28, 2005)

Thanks Dick,
I couldn't figure out how to link directly to the page, kept putting my address in the link. 
Thanks for doing that. 
We just had our general meeting where Randy reported on his OA findings as well as Almond Pollination. I did my reports on Powdered Sugar. We are not at odds with each other, Randy has given me so much support and time, but he still strongly feels I should do some OA treatments before winter, and I strongly feel I need to continue just using powdered sugar. 
He does want to do some powdered sugar experiments, but he also has low mite counts, and he has around 500 hives. He asked at the meeting for hives with high mite loads so he could do some experimenting on them. No body came forward. Pretty good for a whole club. They are using either OA or powdered sugar and we are all seem to be in great shape.
Yesterday we removed our honey supers for extractions and did a sugar dusting. We have wall to wall brood on all 8 hives. I'll remove the sugar this morning and report on it later today.
Thanks again,
Janet


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## Dick Allen (Sep 4, 2004)

Janet, our bee packages, for the most part, come in from California. I can usually leave them untreated the first summer and get them through winter. It's mid to late summer next that pms, phoretic mites, deformed wings show up. 

As I wrote earlier in another thread I did powder one overwintered hive every 10 days to 2 weeks a year ago using the BWrangler "varroa blaster", but that hive did succumb to mites as did those overwintered hives treated with Sucrocide every 10 days to 2 weeks. Next summer I'll try sugar dusting weekly your way. On some hives last season I did vaporize OA into them to no avail, but I had problems doing that--getting the crystals to vaporize, etc. Some of my hives were requeened earlier this past summer with those Nebraska queens from MB. Those will be not be treated with anything this season, but my other hives will have OA drizzled on them after brood rearing stops.

[ September 07, 2006, 11:35 AM: Message edited by: Dick Allen ]


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## honigbiene (Sep 6, 2006)

How does the sugar dusting work? Does it just physically dislodge the mites so that they fall to the floor of the hive? If so, wouldn't the mites just search out a new host? Or does it kill them somehow?

Janet said, "I'll remove the sugar this morning and report on it later today". 
I'm assuming this refers to the sugar that fell all the way through to the floor. How do you remove the sugar? It seems that removing the sugar containing dislodged mites that are still alive is necessary, or if they are dead, to count them. Is this why the sugar is removed?


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## drobbins (Jun 1, 2005)

David

you use a screened bottom board so the mites can fall out of the hive
you're correct in how it works
you also want to catch the sugar that falls out so you don't attract ants

Dave


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## 2rubes (Apr 28, 2005)

Hi David,
The only way the powdered sugar seems to kill mites is by suffocation. You can see a great deal of dead mites' coated with sugar, you also see live mites walking on top of the sugar. Dr. Eric Mussen, UC Davis says he pulls out mites coated with sugar and they are alive and thats what he uses in his experiments. 
I have seen mites on top of the sugar jump on bees that land on the sticky boards as Im carrying them to a table. It happens so quickly. I know keep powdered sugar that I can sprinkle on those bees. The sugar gets on the mites sticky pads and they can not latch on to the bee and become easily detached.
I remove the powdered sugar from the hives on the sticky boards and after taking pictures, I scrape the sugar into a plastic trash bag. I leave the bag under a tree close by. The next day, you can see a line of ants removing the mites. They are not touching the sugar. Between sugar treatments, we leave the boards out for ventilation and you can see ants under the hive, but we havent had any inside. 
I havent had time to count mites in the powdered sugar. Im trying to blow up the pictures we took the other day and get them posted, but its been a bit hectic around here lately. There were 100s of mites in the powdered sugar, not 1000s like last year. The one hive that had been in the shade that had our highest 24 count of 20 had the most mites in the sugar. I have the boards in right now and will check them this morning, but this would not be an accurate count, since the bees groom themselves for several days. Mostly curious to see how many drop off immediately after a powdered sugar treatment.
Dick, Randy Oliver is thinking the best way to remove high mite load before winter would be to dust them intensely every 3 days for several weeks. He feels that newly hatched mites would need to feast for at least 3 days and this would capture most of the emerging mites. He also mentioned that you could do the powdered sugar like this just once in August, but Im not agreeing with that. Doing a treatment in the spring and then once in early summer and then again in August, keeps the mite counts low and you dont have to struggle in August with real intense treatments. 
Janet


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