# OAV treatment efficacy over time



## Eikel (Mar 12, 2014)

Check Randy Oliver's website where he discusses OAV efficacy (http://scientificbeekeeping.com/oxalic-acid-heat-vaporization-and-other-methods-part-2-of-2-parts/ ); it's not a quick, single kill. It's impact on phoretic mites is like 25% on day 1, 75% on day 8, 85% on day 15, etc.


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## Tenbears (May 15, 2012)

Oxalic Acid only stays within the hive for a relatively short time. When used during a brood free time it effectively reduced the breeding population significantly enough that it can take months for them to rebound. One must however consider that if one is in an area where there are significant numbers of mites then the odds of repopulation even in a mite free hive would be increased. By treating when brood free or a regimen that facilitates exposure to the majority of the mites prior to winter, when bee flight is minimal and contact with outside bees infrequent. One can arrive at spring build up with healthy bees.


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## Thomassen (Jul 6, 2014)

Thanks for the info.


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## laketrout (Mar 5, 2013)

Its seems like everyone is in agreement on the positive and needed treatment of oav at the end of the year to get the higher percent kill rate when there broodless . But what about the Spring, I would think it would be a good time to take advantage of the broodless time again before they start building up .The problem I have seen is they start building up earlier than you would think , they don't wait until the warmer days of April . And then by the time I'm into a good flow the mites are booming and I have honey supers on .

One of the hardest things I have had to learn is getting on a better schedule with my treatments and the flow, taking honey off , and waiting late in the year for the goldenrod to finish up and then get that extracted .


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## DPBsbees (Apr 14, 2011)

laketrout said:


> Its seems like everyone is in agreement on the positive and needed treatment of oav at the end of the year to get the higher percent kill rate when there broodless . But what about the Spring, I would think it would be a good time to take advantage of the broodless time again before they start building up .The problem I have seen is they start building up earlier than you would think , they don't wait until the warmer days of April . And then by the time I'm into a good flow the mites are booming and I have honey supers on .
> 
> One of the hardest things I have had to learn is getting on a better schedule with my treatments and the flow, taking honey off , and waiting late in the year for the goldenrod to finish up and then get that extracted .


I think I will treat my production colonies this spring with OAV. The late summer/fall flow was so good this year I almost didn't get a chance to get the mites under control. It may not be the same this year, but I don't want to have to miss a crop to take care of the mites so I'll start the spring relatively clean so I have a fighting chance. They'll get a dose the first 40 degree day in March. I'll have MAQS at the ready should I need to deal with them with the supers on.


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## enjambres (Jun 30, 2013)

@Laketrout,

I don't know when you're thinking there is a broodless period in the spring. My hives, up here north of Albany start their brood cycle again in late January/early February. Probably earlier than that in PA?

Since OAV has a high kill rate when all the mites are phoretic, and between now and then there is very little flying, drifting, robbing, etc., there's no way for more mites to come in the hive. And without brood there can be no increase in mites. So what you have after the last ones are killed by the December OAV is what you have when they start brooding again in six to eight weeks.

However, I think this year will be the exception that proves the rule. If you treated your hives in around Thanksgiving (the usual suggested time in the north) then we had a month of warm weather, including many days warm enough to fly long distances (not just out to poop and back) I think there is a good possibility that treated/cleaned up hives could have been reinfested with fresh mites from untreated or feral colonies.

For various personal reasons my broodless treatment has been delayed and I have not yet done it (I usually shoot for the Solstice-to-Christmas period) and I'm happy it worked out that way. Next weekend will be warm enough enough again, so I plan to do my "December" treatment, and this will kill any new recruits my bees have acquired recently.

I note that the OP is CA and presumably has brood most of the time. OAV in a hive with brood is, at best, a suppression tactic, not a clean-up type of treatment. That's not to say it's not worth the effort, but to isn't going to kill the mites off completely. You'll just be lowering the numbers to a point where they will not (for awhile) be too big a problem.

Enj.
s


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## Mike Gillmore (Feb 25, 2006)

enjambres said:


> However, I think this year will be the exception that proves the rule.


I think so too. 

I typically do my winter OAV treatment around Thanksgiving, but because of the extended warm weather this Fall I waited until December 6th. Then we had another month of unseasonably warm weather in December. Up until about a week ago the bees were flying more days than they were not. I'm thinking about doing another treatment very soon, just to be sure the mites are under control. One treatment in mid winter during the broodless period is usually enough, but this has been a very unusual winter.


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## laketrout (Mar 5, 2013)

Dan I like your idea of the first warm day in March for a treatment, maybe I won't get in trouble with mites skyrocketing right when I'm in a flow with supers on . I'm in Pa also just a couple hours north of you the temps should be pretty close . Even though there will be some brood development by then this treatment should get the bee's through into late summer and maybe even into the goldenrod flow not sure .I'm building some screened shims to put on top of my solid bottom boards so I can keep better tract of mite counts and also easier oav treatments from the back of the hive .

Dan did you treat this past March or is it something your going to try in 2016 .


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