# Varroa Mite Drop Threshold



## Matt Guyrd (Nov 28, 2007)

For those of you that perform 24-hour mite drop counts, what is your "economic threshold" at which you feel some sort of action needs to be taken?

And how did you come up with your threshold?

Thanks.
Matt


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## Michael Bush (Aug 2, 2002)

I'm more interested in the trend and the proportion than a magic number. If you have a small struggling hive dropping 50 mites in twenty four hours and the numbers have been rising, that's a bad situation that needs to be dealt with. If you have a booming hive that is dropping 50 mites in twenty four hours and the number has been steady, I might not panic yet, but I'd keep an eye on it.


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## Chef Isaac (Jul 26, 2004)

michael: even with your small cell, do you do mite counts?


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## Michael Bush (Aug 2, 2002)

>michael: even with your small cell, do you do mite counts?

Up until I wasn't finding any mites anymore, yes. This last year I just couldn't find hardly any anymore, so I finally quit. How will you know if it's working if you don't count?


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## Dave W (Aug 3, 2002)

Mites die/drop off of bees at very different rates througout the year.
The "magic number" called "economic threshold" depends on the time of year the count is taken. This time of year, a hive can have w/ low numbers and have LOTS of mites in capped brood, BREEDING MORE MITES! Is a daily count (this time of year) of may 5, 10, 20 below "economic threshold"?

Your best bet, is to count several times at regular intervals over the next few months.
You will see a point in time when a steady rise occurs (a 1000% increase over 60 days), then you will know "its time" to "CONTROL THE MITES".


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## golddust-twins (Sep 8, 2007)

*Question for Michael Bush*

>>michael: even with your small cell, do you do mite counts?

>Up until I wasn't finding any mites anymore, yes. This last year I just couldn't find hardly any anymore, so I finally quit. How will you know if it's working if you don't count?

Michael, How may years have you been on small cell? I am just starting small cell this Spring and do counts 3 times a week. I intend to keep counting like this till I see something different. Just wondering how long (years) you counted till you saw virtually no mites? So far my counts have been quite low compared to what I was experiencing this past fall and early winter, ( 0 to 3 mites per 2 days). I realize it is early in the season and the mites will pick up as we swing into summer so I am keeping a close watch.

thanks,
Corinne


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## Michael Bush (Aug 2, 2002)

>Michael, How may years have you been on small cell?

I started in 2001 but didn't really get any regressed until 2002.

> I am just starting small cell this Spring and do counts 3 times a week.

I think that's overkill. Once a week is pretty often. Once a month isn't that bad.

> I intend to keep counting like this till I see something different. Just wondering how long (years) you counted till you saw virtually no mites?

The numbers went down as soon as the cell size did, but there were always still some mites. Two or three in a 24 hour drop for several years. This last year (2007) was the first time I actually couldn't find any mites.

> So far my counts have been quite low compared to what I was experiencing this past fall and early winter, ( 0 to 3 mites per 2 days). I realize it is early in the season and the mites will pick up as we swing into summer so I am keeping a close watch.

Sounds good so far.


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## golddust-twins (Sep 8, 2007)

Thanks Michael

Corinne


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## Aspera (Aug 1, 2005)

*Happy Thoughts vs. Couphamos vs. Other*



Dave W said:


> Mites die/drop off of bees at very different rates througout the year.
> The "magic number" called "economic threshold" depends on the time of year the count is taken. This time of year, a hive can have w/ low numbers and have LOTS of mites in capped brood, BREEDING MORE MITES! Is a daily count (this time of year) of may 5, 10, 20 below "economic threshold"?
> 
> Your best bet, is to count several times at regular intervals over the next few months.
> You will see a point in time when a steady rise occurs (a 1000% increase over 60 days), then you will know "its time" to "CONTROL THE MITES".


Just out of curiosity, what is your favorite method of "controlling" mites?


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## Dave W (Aug 3, 2002)

>what is your favorite method of "controlling" mites?

One of my favorite, Apistan. Nothing (thats legal) kills like Apistan.

Second best; brood trapping/queen caging/brood removal/splitting.

Aspera its great to hear from you.

What's your favorite?


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## Michael Bush (Aug 2, 2002)

>One of my favorite, Apistan. Nothing (thats legal) kills like Apistan.

It hasn't worked here since the 90's.


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## Aspera (Aug 1, 2005)

Lately I've been aggressively culling comb and requeening with SMR/Russian/Hygienic stock from Tom Glenn. This basically amounts to the same as splitting and brood cycle interruption. Last year I had some success with Api-Life but decided to just watch them crash as they may this summer. The real problem that I'm running into is that my Russian/SMR stock had relatively low fecundity and does not draw new comb as a result. I may have to take a step backwards and use less VSH/SMR so I can get rid of more garbage comb. The Minn Hygienics may be the way to do this. Apistan still works for me (as far as I know) and I might use it as part of IPM strategy this fall, but I want to test the colonies this spring. I suspect my "boomers" will crash in 3 months.


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## Dave W (Aug 3, 2002)

>I suspect my "boomers" will crash in 3 months . . .

Dont you think, a "brood interruption" now (or in a couple of months) would "hold" the boomers until mid-August, when (after harvest or "a" harvest) they could be treated for winter?


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## Aspera (Aug 1, 2005)

Sure, but I want to determine if any colonies can survive and be productive with minimal intervention and my comb culling probably has already significantly interrupted the brood cycle for some of these colonies. Many on this website say that mite survival without treatment is possible, and being a hobbiest means that 50% colony losses are not a big deal for me. So I'm going to see how far I can push the "no treatment" envelope.


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