# OAV with brood, seeking studies



## Grins (May 24, 2016)

I'm new to beekeeping, started this year. I haven't posted much because I usually find the answers by reading through the threads here, thank you to all the posters. 

I'm using OAV for mite control, bought a varroa cleaner and am quite happy with it. I've read a ton on this forum about frequency and 3 or 4 treatments 6 days apart seems to be the consensus when brood is present. 

However, Bernhard Huevel posted this comment back in March, "_With lots of brood present you need another interval to make OAV working. Three days apart(!), six times at least. Check again and treat a seventh time if necessary. Mites are not stupid, they hide away in cells when they are about to be killed. So you need to repeat the treatment more frequently. With the right vaporizer you don't harm the bees at all._"

I'm looking for studies to support either the 6 day interval, or the the 3 day interval. Here is an excellent study done without brood and this is in the vein of what I'm seeking. This was posted here by Bernhard, and I thank him. http://www.tandfonline.com/doi/pdf/10.1080/00218839.2015.1106777

Thank you all, I've learned so much keeping my mouth shut, my eyes open and reading.

Lee


----------



## emrude (Mar 23, 2015)

Good question. I have just started thinking about starting OAV treatments on my hives. I did the three times 6 days apart last year. I have brood. I will pull the honey supers before treatment. We should have a fall flow so it ain't over yet. 

Mary


----------



## enjambres (Jun 30, 2013)

Lee,

In the US the product is labeled for use on bees to kill varroa, and I believe the US labeled dosage is one treatment every 7 days, times three. And in the US pesticide applicators get it drummed into their heads that "the label is the Law."

That being said, I have to confess to a) having started using it before it was approved in the US or my state (NY) and b) using it for more than three times in a row, and sometimes at slightly different intervals. 

I actually preferred the old four treatments/five days apart regimen over the current one. One of the problems that occurs to me with the six-dose, every three days is that it just barely cover a full drone brood cycle. There could be some drone brood, the preferred host of varroa, who would escape treatment exposure both at the beginning and the end.

I'd suggest starting with the "standard dose" and maybe repeating it immediately if tests show it's not doing the job for you.

I spent some time last winter modeling the various effective exposure periods, kill rate percentages, phoretic period latentcy, pupal stage lengths and trying to concoct a decent model to predict efficacy, No matter how I jiggered things, it still was, on paper, a pretty big stretch to get good effectiveness when there was a lot of brood in the colony, particularly when varroa levels were high to start. On paper it doesn't look as good as the results that I see, even when they are not as good as I might wish. In other words it looks like it won't work, but it does, but then with brood the effect is quickly negated when fresh ones hatch out.

It's a decent knockback treatment at any time of year. But you don't kill enough varroa to clean things out until you get to low or no brood status. At that point it is amazing.

I sometimes use it in the summer when it's too hot for MAQS, and I really need to smack 'em down to protect my earliest winter bees. I use it in a series in the fall to keep on protecting the winter bees, and to prevent flare ups from incoming mites. And I use in late December, early January after flying has ceased, and we have virtually no brood. That's the most important mite treatment of my whole year. And it protects my colonies for nearly six months (and occasionally - this year is one of those - far into the summer.)

I'm hoping some one does a study of it. I'd be very interested.

Be sure to always wear your personal protective gear. it may not kill mites under cappings, but it will sear your lungs if you take a deep breath of it.

Enj.


----------



## Grins (May 24, 2016)

Enj, thanks. I've read quite lot from you on this topic and you are well reasoned and have given this a great deal of thought. There are a lot of things to consider trying to nail this down, I understand that. Broodless colonies are easy.  I'm treating now to knock the mites down before winter and I will treat again when the colony is broodless. I have my calendar set for 6 day intervals but it certainly isn't set in stone. Oh, yeah, I wear the gear. I really like the cost of OAV compared to the others, MAQS is close to five bucks a whack compared to pennies for the OAV. I'm hoping some brave entomologist goes after this issue soon, or better yet the study has been done and someone will post it. I can hope, can't I?

Mary, good luck, and I hope you're Fall flow is great.

Lee


----------



## Harley Craig (Sep 18, 2012)

to know the proper time, you need to know how long it stays active in the hive. Lets say it stays active for 3 days, and you do 5 day intervals that's 2 days worth of hatch and cap for mites to emerge and jump back into a cell. You would have to either examine the comb with a microscope every day to see if the crystals are still present on everything, or possible get a baseline pH with litmus paper then see if it spikes after a treatment then continue to test daily till it drops back down. I would suspect the ph balances out rather quickly and the acid is no longer active. When I tanned hides, a 20 min bath in a base would all but neutralize the acid in the hide, obviously since honey is already a bit on the acidic side, I would assume it would take longer to balance out.


----------



## kaizen (Mar 20, 2015)

unless the hive is broodless or you make it broodless i'm of the opinion that you should pick a certain number of days apart x3 and don't fret about it. unless its done daily you would never get all of them so you're doing a treatment cycle to knock them down. Once the brood starts to dwindle and in spring is the important times to nail them. I try and do them 5 days apart so I can get 2 on a weekend.


----------



## enjambres (Jun 30, 2013)

If I were treating now (and some years I do) I would consider it just a holding action.

And I'd plan on doing a full series (perhaps with one or two additional doses beyond the standard three) starting again in about four or five weeks. The bees will be tapering down on brood by then, with almost no drone cells, so more of the mite population would be vulnerable to my efforts as percentage-in-the-hive-wise, more of the mites would be phoretic. I would also be aiming to keep a lid on any increase of mites brought back to the hive by my enterprising honey-felons in the course of their fall pillaging. 

Last year we had an absurdly long, warm flying period, long after all flowers were gone. I had 72 F on Christmas Eve Day. I was itching to give them my final one-shot dose, but was determined to wait as long as possible to get the flying over with. And then the weather abruptly turned sharply colder, bordering on too cold. Some of my treatment days were less than ideal. I watched the sticky boards very closely and since it appeared there was a slight shift (towards a delay) in the resumption of brood, I took the chance and hit them all again on Ground Hog day. That turned out to be a good move in a wacky winter.

Ordinarily I never have to treat again in the spring after a solid whack of OAV in late December. 

I think you have to be flexible, and thoughtful, about when to use OAV to its best advantage. It isn't at its best if you simply rely on the calendar to tell you when to treat.

I was recently at the NYBeeWellness Conference and there was discussion of using formic acid-saturated cardboard strips, as well as a glycerin carrier for OA. Interesting developments - I'd keep watching Randy Oliver's site for more info.

Enj.


----------



## camero7 (Sep 21, 2009)

I have had great results doing OAV 4X a week apart. It is my standard fall treatment. I'll start this week, as soon as I pull my honey


----------



## Grins (May 24, 2016)

As it turns out Diana Sammataro, author of 'The Beekeeper's Handbook', is an aunt to a friend of mine. As an entomologist her specialty was mites. I'm hoping to hear from her soon and will pass along any useful info I get.


----------



## Tenbears (May 15, 2012)

To determine a treatment regimen we must first understand the life cycle of the mite.

Adult female Varroa mites enter honey bee brood cells (especially drone brood) at the pre-capping stage and lay two to five eggs after the brood cell is capped.
◾0.5 mm long eggs are laid on the bottom of the cells, on the walls, and sometimes directly on the larvae.
◾The first egg laid is a male, and subsequent eggs are female.
◾After hatching Varroa mites pass through two larval stages (called a ‘protonymph’ and a ‘deutonymph’) before developing into an adult. It takes about 5–6 days for male Varroa mites to develop and 7–8 days for female mites to develop.
◾Mating occurs in the brood cell. The male Varroa mite dies inside the cell shortly afterwards. 
◾Young female Varroa mites and the mother Varroa mites emerge from the brood cell with the emerging honey bee.
◾The daughter Varroa mites will lay eggs in other brood cells after 2 weeks. Adult female Varroa mites usually live for 2 months, but can overwinter between the sclerites (the hardened plates of the exoskeleton) of adult honey bees.
the first treatment of OAV gets 99% of the mites outside the cells. The second treatment gets 99% of the mites that have emerged from the capped cells. Since those emerged do not lay eggs for two weeks they do not enter cells ready to be capped during that time. thus there are no mites in cells capped between the first treatment and the second providing two weeks have not elapsed. The third treatment kills 99% of the mites that emerge from the reaming capped brood.
Since drone brood is capped the longest at 10 days +-1 then any treatment that spans that time frame will do the job effectively. In fact an initial treatment followed by a second treatment 12 days after would offer sufficient protection for the hive. Since the build up of mites is exponential it normally takes three years for mites to grow into what one would consider an infestation. With this in mind one can reasonably conclude that a single annual treatment done properly will effectively reduce mite loads to maintain the health of the hive. Mite load monitoring at the 6 month mark would indicate increases that a given individual can evaluate to determine the necessity of additional treatments. i


----------



## beemandan (Dec 5, 2005)

Harley Craig said:


> for mites to emerge and jump back into a cell.


This issue has been discussed before.....but please don't ask me to find the thread. My memory of it is that a mated female mite requires several days after emerging from a cell before infesting another. For the original foundress mite it is probably a recovery interval. For the newly mated mites it is probably a maturing interval.
Edit: or what tenbears wrote.


----------



## Grins (May 24, 2016)

Thanks Tenbears! Yours is a great argument for 3 treatments 7 days apart. I appreciate the life cycle info, condensed like that it helps me understand.

Lee


----------



## beemandan (Dec 5, 2005)

Grins said:


> Yours is a great argument for 3 treatments 7 days apart.


I do think that the foundress mites can reinfest in a matter of a few days. Personally...I'd want the treatment interval a little shorter.


----------



## Bob J (Feb 25, 2013)

Great discussion.... Last year I treated OAV in all my production hives (10) on a 5 day cycle in August right after I pulled my honey.... I monitored mite drop every day for the first two cycles.... What I observed was that the first day after treatment there was very little drop with a very big drop the second day... For each successive day after that I observed roughly half the mite drop of the previous day even though I assume the mites were continuously emerging from the capped brood... After 4 days it dropped to pretty much the background noise level for the hive pre treat... Based on this (albeit anecdotal) evidence I concluded that the effective exposure period for a single OAV treat when capped brood is present to be approximately 4 days.... 

Treatment vs treatment day 2 drops varied significantly for the first 5 cycles (much more than I expected) which I assume is related to variations in how much brood was emerging during the cycle.... After 5 cycles it dropped significantly but for several hives was still large enough to justify treating for 2 more cycles... After that it became effectively negligible....

One more observation is that I continued to monitor natural mite drop on a weekly basis with great results until the third week in September when one hive suddenly showed a significant number of mites again. I treated that hive twice to knock the mites back down. My assumption was that they robbed out another hive in the area that was collapsing.

I treated all hives one more time around Halloween and observed negligible day 2 mite drop. All hives overwintered successfully....


----------



## beemandan (Dec 5, 2005)

*The phoretic stage lasts about 5-11 days when there is brood in the colony.*
http://articles.extension.org/pages/65450/varroa-mite-reproductive-biology


----------



## beemandan (Dec 5, 2005)

Bob J said:


> Based on this (albeit anecdotal) evidence I concluded that the effective exposure period for a single OAV treat when capped brood is present to be approximately 4 days....


Everything I've read....and my experience suggests that oav doesn't kill mites immediately. My midwinter...lowest brood time.....single treatments didn't start to drop significant numbers of mites for a number of days after the treatment.


----------



## Grins (May 24, 2016)

beemandan said:


> Everything I've read....and my experience suggests that oav doesn't kill mites immediately. My midwinter...lowest brood time.....single treatments didn't start to drop significant numbers of mites for a number of days after the treatment.


Yeah, it's another moving part to consider. I've read the OA damages mite organs once absorbed through the damaged 'feet'. I guess it raises another question, are these mites exposed to OAV capable of laying eggs? Or are they simply dying a slow death after exposure.

Thanks for the link, good stuff.

One more edit, this study would lead me to think 5 day intervals for OAV would be most effective.


----------



## viesest (Jul 13, 2016)

I also think that treatment every three weeks from July to December can fulfill two goals. One is keeping low infestation in summer, and second is rid of varroa mite in fall, as much as possible. 

Note: Effect of treatment once every three weeks
http://scientificbeekeeping.com/2016-oxalic-acid-pdf/


----------



## Grins (May 24, 2016)

viesest said:


> I also think that treatment every three weeks from July to December can fulfill two goals. One is keeping low infestation in summer, and second is rid of varroa mite in fall, as much as possible.
> 
> Note: Effect of treatment once every three weeks
> http://scientificbeekeeping.com/2016-oxalic-acid-pdf/


Looks to me like once every three weeks would be barely controlling mite population. Every week for 4 weeks appears far more effective to knock the population down as a mid season treatment.


----------



## viesest (Jul 13, 2016)

Grins said:


> Looks to me like once every three weeks would be barely controlling mite population. Every week for 4 weeks appears far more effective to knock the population down as a mid season treatment.


Yes it looks a bit weird, bat every three weeks is a nice pace for checking how is varroa doing in summer. If it is blooming then "Every week for 4 weeks" treatment for lowering infestation. In autumn it is for aiming brood less period which is not necessary in all hives at once.


----------



## dudelt (Mar 18, 2013)

There are some great replies here. Last December was the first time I have done a winter OAV treatment. Every other year by early August, you could easily see the pre-treatment varroa drop on the screened bottom boards in large numbers. This year, there is almost nothing. In my opinion, the winter treatment is the key. Every other treatment is just holding the numbers down so you can get to the winter treatment. In my area, this time of year there is not a lot of drones hatching. If you miss one days worth of drones with the treatments, it is not much of a problem. Finally, I started my August treatments yesterday! I was only able to do 3 of the 12 hives but it was a good start.


----------



## Grins (May 24, 2016)

There are two important numbers to consider. The length of time a mite is in a capped cell, and the length of time it is phoretic. 14 days is the length of time a drone cell is capped so the duration of all treatments should slightly exceed that. Mites are phoretic for 5 to 11 days.

For the sake of simplification I'm assuming OAV is immediately effective (it's not but the time cycle would not change) and that OAV has no residual effects. So,

Day 1- All phoretic mites killed, newly capped drone cells start clock ticking for 14 days
Day 2- Emerged adult bees with new phoretic mites. We have 5 days to kill them before they move into a cell.
Day 5- OAV kills all newly emerged mites since last OAV
Day 10- Ditto
Day 15- Ditto plus all mites emerging from the drone cells capped just before first OAV

It seems to me 4 treatments 5 days apart would be the most efficient way to knock varroa down during brood.

And hit em again when broodless in the late fall, early winter. 

Lee (I am a mental gymnast and spend waayyy too much time over-thinking things, but it keeps me off the streets.) :scratch:


----------



## beemandan (Dec 5, 2005)

Grins said:


> this study would lead me to think 5 day intervals for OAV would be most effective.


I think this would be my target if I were using oav as an active season treatment. I think that 3 treatments 5 days apart ought to expose most of the mites.


----------



## Grins (May 24, 2016)

beemandan said:


> I think this would be my target if I were using oav as an active season treatment. I think that 3 treatments 5 days apart ought to expose most of the mites.


Yeah, the 4th treatment would nail the buggers that were in the drone cells capped as I was putting my respirator on for the 1st treatment.


----------



## beemandan (Dec 5, 2005)

Grins said:


> Yeah, the 4th treatment would nail the buggers that were in the drone cells capped as I was putting my respirator on for the 1st treatment.


It would be interesting to put a sticky sheet on the bottom, replace it at each treatment and watch the trend. I'm betting that you'd discover that the fourth round was unneeded. But....that's just my guess.


----------



## Grins (May 24, 2016)

beemandan said:


> It would be interesting to put a sticky sheet on the bottom, replace it at each treatment and watch the trend. I'm betting that you'd discover that the fourth round was unneeded. But....that's just my guess.


I think you're probably right. The only phoretic mites would be on the drones emerging from the cells capped the day before the first treatment. How many would that be? 

Lee


----------



## snl (Nov 20, 2009)

Grins said:


> For the sake of simplification I'm assuming OAV is immediately effective (it's not but the time cycle would not change) and that OAV has no residual effects


It is, but it does have residual effects.......it will continue to kill until it is carried out of the hives by bees in about 3 days (who see it as trash)...
Day 1 - Most phoretic mites killed.
Day 2 - Many Emerging mites killed (yes, some will enter brood about to be capped)
Day 3 - Many Emerging mites killed (yes, some will enter brood about to be capped)
Day 4 - Mites emerge with brood .... enter phoretic stage
Day 5 - Mites emerge with brood .... enter phoretic stage
Day 6 - Mites emerge with brood .... enter phoretic stage
Day 7 - Next treatment - most phoretic mites killed prior to entering brood about to be capped.

3 Treatments cover the brood cycle... You will never get all mites during brood rearing. But......... you'll knock the devil out of them until you get them all during the broodless period.
Now is the a great time to treat. You want healthy bees raising health winter bees ........ who will keep the hive alive.


----------



## Grins (May 24, 2016)

snl said:


> It is, but it does have residual effects.......it will continue to kill until it is carried out of the hives by bees in about 3 days (who see it as trash)...
> Day 1 - Most phoretic mites killed.
> Day 2 - Many Emerging mites killed (yes, some will enter brood about to be capped)
> Day 3 - Many Emerging mites killed (yes, some will enter brood about to be capped)
> ...


Yep, the residual period makes a 7 day schedule doable but the emerging bees with mites have no OA on them, the mites would have to switch hosts and land on one with crystals. I'm sure the 7 day schedule would knock them down sufficiently while we all wait for the broodless time though.


----------



## snl (Nov 20, 2009)

Grins said:


> Yep, the residual period makes a 7 day schedule doable but the emerging bees with mites have no OA on them, the mites would have to switch hosts and land on one with crystals.


The emerging mites after day 3 will stay phoretic until the next treatment.......... then it's open season on mites again!


----------



## Grins (May 24, 2016)

snl said:


> The emerging mites after day 3 will stay phoretic until the next treatment.......... then it's open season on mites again!


Vance G, a member here became my mentor as I began beekeeping this year. He has hammered into me since day one the importance of varroa control. I'm a believer. It was reinforced by a friend in Salt Lake City who lost his colony to the little offenders. Varroa mites are always on my mind and the open season never closes. 

Lee


----------



## tulsafarmer (Feb 28, 2016)

following


----------



## tanksbees (Jun 16, 2014)

Grins said:


> I really like the cost of OAV compared to the others, MAQS is close to five bucks a whack compared to pennies for the OAV.


It takes at least 10 minutes to suit up and get power and OAV a hive and you have to do it 4 times.

So that's 40 minutes a hive. Standing in the sun. With a gas mask and bee suit on.

$5 to save 40 minutes - good value.


----------



## Grins (May 24, 2016)

tanksbees said:


> It takes at least 10 minutes to suit up and get power and OAV a hive and you have to do it 4 times.
> 
> So that's 40 minutes a hive. Standing in the sun. With a gas mask and bee suit on.
> 
> $5 to save 40 minutes - good value.


Bwah, Hah, Hahahaha..., you're right, of course! However, I'm in the retired class, time is not as valuable as it used to be so I have the luxury of not viewing it that way. Also, I gas early in the morning, nice and cool. You make a really good point though, if one has many hives MAQS can represent a good value.
Lee


----------

