# How long after an OAV treatment does the most significant mite crop occur?



## Eikel (Mar 12, 2014)

Nancy,
This will obviously not answer all your variable questions but Randy Oliver does have some research on OAV efficacy.









http://scientificbeekeeping.com/oxalic-acid-heat-vaporization-and-other-methods-part-2-of-2-parts/


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## Ruthz (Sep 13, 2011)

Here is my anecdotal experience. I have an observation hive with 2 deep frames that I put some bees in last November when, despite treatment, it became clear that the nuc was going to die. As a Hail Mary attempt at saving the queen and remaining bees, put those remaining bees into the observation hive. Once observed carefully, these bees were covered in mites and full of diseases, DWV and Paralysis virus of some sort. (Mite bomb?)

Anyway, I treated the observation hive on a 30 degree F day in late Novemeber with wood bleach OA from Home Depot, using the ProVap100, through a small hole at the bottom of the hive, with a 1 gram dose (way too much for 2 frames). As I watched the vapor float around, get fanned by the bees, and eventually crystallize on the frames, etc. I noticed that the bees did not seem overly upset by this situation. I thought there would be panic or chaos, but the bees were quite calm. The bees were located in a big circle spanning the two frames. There were all stages of brood on the frames. I had completely vacuumed out the hive floor before treating, because I was curious about counting the mites.

Anyway, maybe 6 mites dropped that afternoon. I was disappointed. 24 hours after, there were about 20 mites on the floor. I start questioning my methods thinking about what I might have done wrong. I could still see mites firmly attached to the bodies of many bees. By 48 hours, there was a reasonable covering of mites on the floor, and by 36 hours, the mites had rained down getting stuck between the glass and the over-full honey part of the frame, forming a line of dead mites about 1/2 cm thick. I could not believe that that many mites could have existed on so few bees (relatively speaking). So the difference in mite drop between 48 and 36 hours was huge.

I think the 36 hour mark is probably the best measure of the mites killed by the treatment. The initial 6 mites after 24 hours were probably just mites dying of old age.


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## Mike Gillmore (Feb 25, 2006)

_a) do you use a sticky board or tray under a screened floor or are you observing dead mites on the solid floor of a hive._
I use a tray under a screened bottom board.

_b) what type of sublimation (not fogging) equipment used_ 
Varrox Vaporizer

_c) dose given in total grams_
2 g per 3 mediums

_d) kind of OA: official stuff from bee suppliers, Savogran Wood Bleach, or chemical supply source_
Savogran

_d) size (8- or 10- frame and medium or deep) and number of boxes in stack at treatment_
10 frame mediums. 3-4 boxes at treatment time.

_e) position of most bees in the colony at time of treatment_
Winter broodless treatment - top half of the stack. Fall series - All boxes.

_f) point of delivery, i.e. top or bottom_
Bottom, under screened bottom board

_g) estimated amount of brood_
Winter - 35,000+ Fall - 50,000+

_h) time of day (i.e. most bees inside during treatment, or many foraging outside)_
Early morning before sunrise. All bees inside.

_i) outside air temps_
Fall - 70 deg+ Winter - 45 deg+

_j) what is the pattern that you observe in mite-drops after treatment: at 12/24/36/ or more hours? _
Heaviest drop after first 24 hours. Most fall after the first 48 hours, then I'll notice a rapid decline in numbers.


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## Richinbama (Jan 15, 2018)

Mike and Ruth'z, thanks for posting this. Last 2 comments !!! I'm curious, shout this oa treatment be done on a 6 or seven day rotation for 3 times. To catch all stages of brood bee cycle? Newbee here..


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## enjambres (Jun 30, 2013)

*@Eikel*,

Thank you for the link. I had seen it, but it's always great to get more exposure for Randy Oliver's excellent site. 

I am not looking so much for long-term OAV efficacy with this question as much as what is the immediate, short term evidence of dead mites on sticky boards on the floor of the hive, and when does the maximum effect become apparent. I was surprised that some people were reporting a much quicker drop than I usually see.

Have you played around with Randy's new mite population estimation tool? It's sobering.

*@Ruthz,*

Thanks for your report, so you would be "late dropper", right? A half-inch band of mites would set my hair on fire, though I am sure it was very gratifying to see it in the end. I hope your colony is still hanging in there.

I chuckled when I read this:


> I was disappointed. 24 hours after, there were about 20 mites on the floor. I start questioning my methods thinking about what I might have done wrong.


Because that is _exactly_ how I think, too. What have I screwed up, now?

*@Mike,*

Did you really mean you have 35K of brood in winter? I am assuming you meant bees? Which brings up a good point - I don't have any question in my list about the size of the colony. 

You are reporting being a "late dropper", too, i.e. between 24 and 48 hours, or do you see the largest drop after 48 hours? 

Thank you for making such a thorough report.

*@Richinbama*,

The labeled treatment is a three-part series of doses done when there is no brood and no supers on the hive, at seven day intervals. In other words, treating on Day 1, Day 8 and Day 15.

Many of us who have been using OAV since well before it was approved have a somewhat more free-form practice, which technically puts us in violation of the law, since with pesticide usage, "the label IS the law." As you gain more experience with bees you may decide to use OAV, but you should do research to find out why some people use non-standard practices before you launch into using doing anything other than what was approved. And be sure to always use the required personal protective gear, which is at a minimum a half-face respirator with ACID GAS canisters and goggles if you are using a wand, like a Varrox or a band heater. If you use a ProVap, you will need a full face respirator, with the same type of canisters and heavy gloves. 

Nancy


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## Mike Gillmore (Feb 25, 2006)

enjambres said:


> *@Mike,*
> 
> Did you really mean you have 35K of brood in winter? I am assuming you meant bees? Which brings up a good point - I don't have any question in my list about the size of the colony.
> 
> You are reporting being a "late dropper", too, i.e. between 24 and 48 hours, or do you see the largest drop after 48 hours?


Whoops, I need to slow down and read more carefully. Yes, I was estimating bee population. 

The single dose between Thanksgiving and Christmas - I have very little or zero brood in the hive. 
Fall treatments -they are brooding up again with wintering bees and I would expect to find about 10+ medium frames with brood in various stages. 

I no longer count mites on the boards, but I can estimate approximately how many mites are there based on endless afternoons in the past counting mites on sticky boards. I'm sure you understand. 

Without having exact numbers I would guess that about 60% fall on the first day, 20% more after 48 hours, and then the numbers taper off fairly quickly after that. I will take a look at the boards after 24 hours, but 48 hours seems to be the peak, and that will be my gauge as to what is happening in the hive.


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## enjambres (Jun 30, 2013)

Mike,



> based on endless afternoons in the past counting mites on sticky boards. I'm sure you understand.


I do understand, boy, do I!

So if I am reading you right, you have 60% of the mites in the first 24 hours, and over the next 24 hours you get another 20%, right. So you would be more of an "early dropper". 

I often am nonplussed by seeing next to no mites in the first 24 hours. In fact when I treat someone else's hive I always caution them NOT to expect any results until late in the second day. Because otherwise they often call me up and want me to come back and repeat the treatment since it obviously didn't work as fast as spraying Raid at a ****roach.

I generally use a Varrox wand, too, but I have a brand new ProVap that I was thinking of putting into service next week. I may do an A/B test through this series to see if there is any discernable equipment-based difference in the pattern of early/late dropping. All of my bees are in the same size stacks, though some are still showing the aftermath of their bout with EFB last summer in being much smaller clusters.

Nancy


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## Richinbama (Jan 15, 2018)

Thanks Nancy, I do thank you for going into detail there. I'm looking to do o av, or I think it's cosmic pro strips after about 1 - 2 weeks after packages are in ,or swarms caught. Is this a good idea. One or the other, not both. Id like a good start on this or a full program as i progress. Whats the best, and whick qould you do long term in your bee yard? 
Thanks, Richard


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## rangerpeterj (Dec 27, 2015)

I allways checked my boards after 48 hrs. This is why I wondered about BeeAurthors calculator? I like the idea but 24 hrs seems short to me.I run 10 frame 2 deeps ,2 grms OA, from the bottom in the morning before bee fly,between Thanksgiving & Christmas,Then a series of 4, 5 days apart in Aug, more if needed.I use a Johno cheapo vac band heater from back of hive ,with bottom slide in on SBB. I do alcohol wash about 3 times a season, more if needed Pete


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## Kuro (Jun 18, 2015)

This winter I saw the peaks of mite drop 3 or 4 days after OAV.

a) Corrugated plastic board (not sticky) inserted from the bottom entrance, not through a screen.
b) Mannlake DC-908
c) 2g
d) Savogran Wood Bleach
d) Double 8-frame deeps
e) In the top deep and in the feeding shim above the top deep.
f) From the bottom entrance.
g) Very little brood but I do not think they were completely broodless.
h) Almost all bees were inside due to cold temp.
i) Outside air temps (see below)
j) what is the pattern that you observe in mite-drops after treatment: at 12/24/36/ or more hours?*(see below)

This past winter I treated my two hives with four weekly OAVs. The first one was probably under-dose, due to the low temperature.

OAV#1 (12/27/17 at <35F). Daily mite counts were ‘2, 2, 5, 20, 3, 1, 2’ in hive A (total 35) and ‘5, 5, 13, 23, 11, 4, 0’ in hive B (total 61).
OAV#2 (1/3/18 at ~40F). Mites counted on day 1, 2, 3, 5, 7. The numbers were ’15, 7, 35, 32, 13’ in hive A (total 102), and ’11, 16, 26, 22, 19’ in hive B (total 94).
OAV#3 (1/10/18 at ~40F). Daily mite counts were ‘9, 3, 11, 10, 4, 3, 2’ in hive A (total 42) and ’20,14, 23,12,10, 8, 8’ in hive B (total 95).
OAV#4 (1/17/18 at 47F). Mites counted on day 1, 2, 3, 5, 7. The numbers were ‘3, 2, 1, 2, 2’ in hive A (total 10) and ‘2, 6, 3, 4, 1’ in hive B (total 16).


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## wildbranch2007 (Dec 3, 2008)

there was a discussion on bee-l about this many months ago which I can't seem to find, but if Nancy doesn't mind I did find this from Medhat Nasa, it covers the drop times for everything but Oxalic but could help someone. I also can't post a link as I'm logged in and in the middle of a search so will just copy the post.

Tim in our lab we do screening for potential miticides. We found in our research that Formic, thymol and hop guard are fast acting products. Formic and thymol require a temperature above 15 C (59F). Hopguard and Apivar do not require temperature. We monitor day 1,2,3 and 5 then we go every 3 days for 42 days. Each time we replace sticky boards. For sure formic acid mitewipe 40ml / pad evaporates in 3 days. Thymovar will last for about 10-15 days. Hope guard only lasts 3-5 days at most. However Apivar has very low drop in the first 3-5 days days based on bee population (1strip for every 5 frames of bees). Apivar stays active for over 30 days up to 56 days. Keep in mind Amitraz concentration in the strip is 3.3% unlike fluvalinate in apistan strips (10%). The low concentration of Amitraz is made to reduce side effects in bees. For apistan when it used to work we would see over 90% drop in the first 3 days.

For hopguard we showed to achieve 80-85% that you need to apply two applications back to back, once every 10 days.

In case each product has its own profile of mite drop.

Hope this helps.

Medhat Nasr


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## snl (Nov 20, 2009)

I have found the largest drop is in the 2nd 24 hours. The bees see OA as trash and readily haul it out when they have the opportunity to fly, due to this OAV is a "flash" treatment, with basically an effective kill time of 3 days. That's why, when there is brood, multiple treatments are required.


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## Mike Gillmore (Feb 25, 2006)

Enj - 



> You know, I almost never see any surge of dead mites until late in the second or even third day after doing an OAV. .....And I use whacking great doses, too, because my stacks are tall. I don't know if it just takes treatment-day killed mites that long to fall down through the screen mesh, or if they die over the days immediately after the treatment due to residual effects.


Copied this from the other thread. How tall are your stacks when you treat? Wonder if you might be onto something regarding the time it takes mites to fall down through the screen if you have a tall stack.

I try to treat with 3 just mediums, maybe 4 at the most, and I get usully get a pretty decent drop after the first 24 hours. Wonder if that makes a difference.


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## dudelt (Mar 18, 2013)

Tray under screened bottom boards, 8 frame deeps, 1, gram per box, Provap 100 and VarroCleaner wand. When it is cold out, I see the biggest drops at day 3, when it is warmer it is on day 2. I believe the temperature make a difference. If the varroa need to step on the crystals to get it under the pads, they need top be moving around too and will not be moving much when it is cold. With the wand, I vaporize from the bottom entrance in the morning. With the Provap, I vaporize from the middle of the stack if more than one box and from the bottom if only one box and usually in the afternoon. I am still killing off the first containers of Savogran I bought a few years back. They were actually on sale so I bought 3 at the time.


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## Kuro (Jun 18, 2015)

dudelt said:


> I believe the temperature make a difference. If the varroa need to step on the crystals to get it under the pads, they need top be moving around too and will not be moving much when it is cold.


That makes sense. Plus, dead mites may be stuck on the comb surface until bees move around and kick them off or remove them. Occasionally I saw a surge (like zero to twenty in a week then back to zero afterwards) of natural mite drop which I thought was caused by spring cleaning activities.


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## shinbone (Jul 5, 2011)

The below graph is for newly hived packages, thus the low mite numbers. OAV was done at 5-day intervals on the noted date. Notice how the hive with capped brood reliably has peak mite drop after 24 hours, whereas the hive without capped brood doesn't show much of pattern.


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## Robbin (May 26, 2013)

snl said:


> I have found the largest drop is in the 2nd 24 hours.


+1 However, I don't treat more than once. I treat once in the spring and once in the fall. Works for me.


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