# OAV Treatment this week?



## LeonardS (Mar 13, 2012)

We will be in the mid to upper 50's by the end of the week in southern Iowa. Are any of you planning OAV treatments with this warm weather? My last treatments were 3 treatments, 7 days apart in mid November to early December.


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## enjambres (Jun 30, 2013)

Did your bees still have brood when you were last treating?

Did you have lots of warm, flying weather after you completed the last rounds when you might have acquired more mites from untreated hives through drift and robbing?

If not, and if your technique was good, then it's not likely there are many more mites to kill at this point.

Mites can't reproduce/increase during periods when there is no brood. And during broodless periods all of the mites in the hive are vulnerable to OAV, unlike during periods of brood when half, or more, of the total number of mites in a colony are protected because they are sealed under the cappings.

That's why a single treatment in the period after Thanksgiving is so effective - because all the mites are vulnerable.

That said, however, if you still had brood, then a series you did was appropriate, especially as it's possible the last treatment coincided to the start of the broodless period.

Late last year was a weird period here in northern NY because we had unusual periods when it was possible for the bees to fly (72F on Christmas Eve Day , for instance) so I think that a very late one-off treatment was advisable. I waited until early January to do my usual "mid Dec. treatment" - and then I had to scramble because it was edging down into too cold, or at least to the lower limits of safe temps. Because I thought that then meant that I might not have had good vapor propagation in the cold, I repeated a round on Ground Hog Day, which I usually do not do.

So the question for you to answer is: do you think your previous treatment cleaned the hives thoroughly (how did your mite drop boards look during and then since then), was there no brood and was there no subsequent way for more mites to be introduced? If yes to all these questions, then I would not treat again at this point. As low-risk as OAV is, there is always some physiologcal, ecological, (in the sense of the hive's ecology) cost to any treatment.

I find that a well-timed broodless period treatment is sufficient to keep mites in check for many months in my area. You can't kill mites that are already dead. I often don't see treatable levels of mites again until mid-summer. 

But I don't rely on my guesses about the mites status: I do mite drop counts every week of the year, and sugar rolls every week of the warm season on a rotating basis through the colonies in my yards. I always have a very good idea of my overall mite status.

Overuse, and unnecessary use, of OAV will hasten its progression to loss of effectiveness.

It is also likely that your hives may have started to brood again - I expect mine are at that stage right about now. So that means that the remaining mites may be once again protected by the cappings (the earliest brood is often heavily infested as the mites are eager to start reproducing again). Unless you knew for sure there was significant mite problem, say in the case of a never-before-treated hive, I would not embark on a series of treatments at this time of year as I think might be difficult to get the needed series of treatment-day windows due to still being in winter temps.

Enj.


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## LeonardS (Mar 13, 2012)

Thank you for the very detailed explanation! I think I will just leave them alone until we have some consistent warm weather.


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## twgun1 (Jun 26, 2015)

I'm a relatively new beekeeper and have not used OAV but have read and listened to a fair amount of information on it. One area I still have confusion with since we are treating late in the fall when brood rearing is shutting down, or there is no brood, aren't the bees that are feeding and raising the winter bees unhealthy from the mites and viruses?


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## Bee Arthur (Mar 21, 2015)

twgun1 said:


> ...aren't the bees that are feeding and raising the winter bees unhealthy from the mites and viruses?


Which is why I'm a proponent of performing vaporizations as soon as the mite count starts to climb up over 2%, no matter how early in the year that happens. Even if you have to remove honey supers for a few weeks in August, to me it's worth it to have a healthy winter population.


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## twgun1 (Jun 26, 2015)

so you can still use oxalic acid in the brooding months,it doesn't hurt the brood right? it just doesnt get the mites under capped cells. Just need to pull off honey supers or blockade them.


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## Bee Arthur (Mar 21, 2015)

I haven't read anything about OAV being harmful to brood. You're right, it doesn't get into capped cells, so you may need to do a series weekly treatments to be sure you're treating bees that were capped when you first start.


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