# OAV with sealed brood--how many treatments?



## Phoebee (Jan 29, 2014)

I will watch this with some amusement. I dove into the old threads on this about a month ago, and my prediction is, if you ask three beekeepers, you'll get five answers. One beek was saying he uses as many as 6 treatments a few days apart. Not the majority opinion, though.

Personally, I used a half dose of MAQS (the mite levels were very low and frankly I could have skipped treatment). Single dose, should knock down most of the mites including those under cappings. In December, when they're broodless, if there are enough mites left to tell, I'll hit them with OAV.

The reason they were nearly miteless this summer was a dose of OAV last December.

Do consider, the official recommendations are to alternate treatments so the mites don't become resistant. Granted, most people here will say there's no evidence they become resistant to either formic acid or oxalic acid, but alternating is still the recommended approach.


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## snl (Nov 20, 2009)

Scrambles927 said:


> That is, for how many days does one treatment stay effective? I have seen different "rules of thumb." Thanks.


In a populous hive, the bees quickly (days) remove the crystals. Basically Oav is flash treatment for as long as it remains in the hive. With the phoretic period of mites of approximately 4-14 days, in a brooding hive, 4 treatments, 5-6 days apart should suffice.


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## Eikel (Mar 12, 2014)

I'm pretty much in line with snl but here's the link to a Randy Oliver article where he provides a table from Thomas Radetzki's research on OA treatment efficacy. The short story is it's not an immediate kill *for phoretic mites *"Radetzki found that mite kill takes place in the first week, and tapers off for the next two weeks."

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


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## Kuro (Jun 18, 2015)

I have not found many data indicating how long OA is effective after each OAV, but in a recent thread (see post #53, http://www.beesource.com/forums/showthread.php?340377-high-mite-drop-after-OAV/page3) where fallen mites were counted daily after OAV, the effectiveness decreased quite a bit after ~3 days (assuming # of emerging mites are constant).


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## texanbelchers (Aug 4, 2014)

There seem to be many schools of thought. When I started the majority said 3 shots 7 days apart. I've been hearing recently people doing 7 shots 3 days apart. I'm in the middle of 5 shots every 5 days; mostly due to my schedule, but also due to my poor results with 3 shots. I think the problem was more on the application than the timing, but 5 shots should keep in OA in the hives more over the entire timeframe.


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## Phoebee (Jan 29, 2014)

And texanbelchers confirms my expectation by providing three options!


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## texanbelchers (Aug 4, 2014)

Yep.  That was the point. The fact is that OAV works. Exactly how I don't know. The mite drops are reported to be highest the first couple of days after each hit with diminishing numbers after that. The biggest issue, as I understand it, is to cover the complete period of a capped cycle to get as many as possible out and exposed.


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## Phoebee (Jan 29, 2014)

Yeah, texanbelchers, I've seen a lot of people here who use three treatments, varying from 5-7 days apart, and I'd go to my bee life cycle poster and what is published about phoretic mites, and figured that just can't be enough.

What got me looking was my mentor, who first got me to try formic acid (using the WVU method), wanted to try my OAV kit. I cautioned him that it is not a one-treatment method when capped brood is present, and that I was not sure the proper interval and number of treatments to get full coverage of the capped brood period. That's why I opted for a half dose of MAQS in August, with one shot of OAV in December. But he wanted to try so he has the rig for now. I think he is going for two doses and it will leave gaps, but if he treats again in December he will probably be OK.

Meanwhile I bought us each 12 ounce cans of OA, because I predict we'll stick with it. You must not go into fall with high mite loads or your bees will be too sick for it to matter, but so far, a single treatment while broodless is just flat out unfair to mites, in my experience.


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## texanbelchers (Aug 4, 2014)

I never go broodless unless I cage the queens. My weather is hot and variable enough to never be able to use MAQS according to the instructions. So, I have limited options.

Of course, I could use powdered sugar dusting, mineral oil fogging, or some other snake oil "if you dream it up, they will die" treatment. But I don't really need to treat because I don't have mites. :lookout:


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## enjambres (Jun 30, 2013)

Last winter I spent considerable time working on a complex mathematical model to determine the best frequency for OAV, based on multiple factors: including (among others) length of the phoretic period of the mites, rate of reproductive success of mites, rate of emerging capped brood, temperature, assortment between drone & worker pupae, assumed duration and efficacy of OA sublimates in the hive, etc. (Oliver's website has excellent data resources for developing such a model.)

It was a complete bust as an analytic tool.

Suffice to say that no frequency was able to mathematically predict successful eradication, or even more than a modest, short-term abatement of the problem. In theory it shouldn't work at all, yet, I know empirically it does.

What I am doing this year is a series of at least four treatments, 5 days apart. Perhaps five, if we continue to have good flying weather. Then I will do one final sugar roll, and bide my time until December when I will hit them again, one last time. It seems to me that that single treatment is what sets the stage for very low mites for the following 9-10 months. But that's the lucky, and local, effect of hitting them when they have already been pretty well treated earlier in the fall (to lower the accumulated mite load), and not significantly re-infested afterward with mites from untreated colonies due to robbing and drifting, and hitting the nadir of the annual brood cycle exactly right, and then having two to three months of complete flightlessness (flightless outside of my treated apiary) due my fierce winter. 

If I am not satisfied with the technical quality of the burns, or if my sticky boards show even a tiny uptick of mites after the broodless period treatment, I sometimes give them a second single dose towards the end of January, weather permitting. I did that last year and my mite counts were exceptionally low this summer. It's not just the hives in my yard - I treated my neighbors' hives with the same schedule, and same reported results. I also treat my students' bees the same way, and they are spread more apart geographically, yet they are reporting the same low mite levels through this past summer. But last winter's weather was profoundly weird up here, which may have been more critical than my OAV routines.

Nancy


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## dudelt (Mar 18, 2013)

Scrambles, The two most common summer/fall treatment schedules is 3 treatments 7 days apart and 4 treatments 5 days apart. Either works well. My preference is the 4 treatment schedule. There are a lot of variables that cause problems. The treatments could be working perfectly but your neighbor who refuses to treat and lets his hives die every year, might be causing your hive to keep getting re-infested. If you are very isolated, a single winter treatment might be all you need. The list goes on and on. As you will see stated all over this forum "Beekeeping is local". What is happening in your locale is unique and it is up to you to figure it out. For example, in New Jersey you may have a couple of months of broodlessness, Texanbelchers who is in Houston, may only have 3 days of a smaller than usual brood nest. 

The general belief is that a single treatment of OAV is effective for about 3 days. While it is not confirmed by any scientific research, I believe the winter treatments are effective for more than 3 days. Because the bees are clustered, and there is very little housekeeping going on, I feel it works a bit longer and is therefore a bit more effective at that time.


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## Mike Gillmore (Feb 25, 2006)

Treatment frequency will vary due to climate and the time period the series is performed. I have been using OAV for about 10 years and been successful with 3 treatments at 7 day intervals starting late August and into September. At this time of year the brood nest is contracted as we are in the latter part of the dearth, and it does a pretty good job of knocking down most of the mites before the winter bees are being raised.

Another single treatment on a warm day between Thanksgiving and Christmas when broodless cleans up the remaining phoretic mites and the colony will be good to go in the spring. 

Try different schedules and see what works best for you in your area.


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## Grins (May 24, 2016)

I treat three times five days apart. I make the assumption there is no residual benefit to OAV. The first treatment hits the phoretic mites. For the sake of timing I assume a phoretic mite emerges with an adult bee an hour after my first treatment. A mite is an adult for between five and eight days. My second treatment kills the mites that emerged in the five days since my first treatment and my third treatment kills the mites that were present in drone brood capped an hour before my first treatment as well as the adult mites that emerged with bees, drone brood is capped the longest at about ten days. Adult female mites live as adults for between seven and eight days so I think a seven day interval gives a few females time to breed and dodge the OAV, not by much, but it seems to me a bigger window that using a five day interval. The key is to do a treatment schedule that will kill adult mites and extend beyond all capped brood cycles. I've kicked around the idea of a fourth treatment but the cost/benefit ratio just isn't there for me.
My two cents, change gratefully offered.


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## dudelt (Mar 18, 2013)

Grins, you have an issue with your math but there is a good reason why your schedule still works well. Drone brood is capped for 14 days. If you treat on day 1, your next treatment is on day 6 and the 3rd treatment is on day 11. You still have 2-3 days of capped brood that was not exposed to the treatment. Any mites in worker brood would be covered. However, one thing that hardly ever gets mentioned is the significance of the dates the treatments are being done. In my area, we treat in early August and in December. By the time August comes, there is very little drone brood in the hives, if any at all. To me, there is so little that it is a non-issue. Since you are just as far north as I am, you may have the same drone dynamics as we do and a 11 day/3 treatment schedule should work just fine.


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## Grins (May 24, 2016)

dudelt said:


> Grins, you have an issue with your math but there is a good reason why your schedule still works well. Drone brood is capped for 14 days. If you treat on day 1, your next treatment is on day 6 and the 3rd treatment is on day 11. You still have 2-3 days of capped brood that was not exposed to the treatment. Any mites in worker brood would be covered. However, one thing that hardly ever gets mentioned is the significance of the dates the treatments are being done. In my area, we treat in early August and in December. By the time August comes, there is very little drone brood in the hives, if any at all. To me, there is so little that it is a non-issue. Since you are just as far north as I am, you may have the same drone dynamics as we do and a 11 day/3 treatment schedule should work just fine.


Wow, you're right! Thanks!


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## Grins (May 24, 2016)

dudelt said:


> Grins, you have an issue with your math but there is a good reason why your schedule still works well. Drone brood is capped for 14 days. If you treat on day 1, your next treatment is on day 6 and the 3rd treatment is on day 11. You still have 2-3 days of capped brood that was not exposed to the treatment. Any mites in worker brood would be covered. However, one thing that hardly ever gets mentioned is the significance of the dates the treatments are being done. In my area, we treat in early August and in December. By the time August comes, there is very little drone brood in the hives, if any at all. To me, there is so little that it is a non-issue. Since you are just as far north as I am, you may have the same drone dynamics as we do and a 11 day/3 treatment schedule should work just fine.


Dudelt, I just want to thank you again for straightening me out about how long drone brood is capped. For some reason I had an entirely wrong number in my head and had based my OAV regimen on these wrong numbers. Now that I have the correct number I have reevaluated my timetable and will be doing three treatments 7 days apart, as many do. I think it will provide better results.


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