varroa lifespan

13569 Views 47 Replies 16 Participants Last post by johno, Jul 26, 2019

olii2d

Discussion Starter · Aug 5, 2014

How long does a varroa mite live?
Also if they fall through a SBB several inches to the ground do they die or crawl back in the hive.
Thank you for any info.

1 - 20 of 48 Posts

Phoebee

· #2 · Aug 5, 2014

I don't know how well they can climb back into a hive, but falling onto a dry IPM board or dry oil tray does not kill them. I've found them on dry trays and they are still crawling around. They move surprisingly fast, too.

They don't seem to be able to climb on slick plastic, although probably can on a porous surface such as wood or block.

Dropping them onto an IPM board (or just a corrugated plastic board from a sign), generously sprayed with veggie oil spray and placed under the screen, is fatal for them, and for SHB as well. This is cheap, easily cleaned off, and gives you your mite drop count.

Michael Bush

· #3 · Aug 5, 2014

They are more mobile than is obvious when you first see them, but falling on the ground is a death sentence. They will not find their way back in.

peterloringborst

· #4 · Aug 5, 2014

Michael Bush said:
They are more mobile than is obvious when you first see them, but falling on the ground is a death sentence. They will not find their way back in.

What possible evidence do you have for this? I have seen varroa crawling all over a table top, they can survive for days outside of a hive and I am pretty sure they can crawl back in from the ground.

Michael Bush

· #5 · Aug 5, 2014

>I am pretty sure they can crawl back in from the ground.

It's always in the details... Maybe if the ground is really smooth and the distance is not far but in my experience the ground is usually not smooth. They are lost in the "jungle." If they are on a smooth tray 3/4" below the screen, they might stand a chance. Plenty of people seem to think that 3/4" is enough... and sometimes it seems it is, but I suspect SOME of those make it back. I don't think any of the ones on the ground have any chance of making it back. They not only have to run that far through obstacles, but they have to figure out where to run to manage to get back in the hive. Neither is likely. Both is even less likely.

Robbin

· #6 · Aug 5, 2014

I saw a study from UF that said Hives standing side by side, one with SBB and the other with regular bottom boards and the SBB averaged 14% fewer mites. So my guess is that a large number of the mites that fall off, don't make it back into the hive. SBB weren't enough to beat the varroa, but 14% fewer was not bad....

peterloringborst

· #7 · Aug 5, 2014

Plenty of people seem to think that 3/4" is enough... and sometimes it seems it is, but I suspect SOME of those make it back.

Yeah, well, plenty of people don't know what they are talking about. 1) I doubt healthy mites fall off the bees very much. Mostly mite drop is dying bees. 2) Healthy mites can travel all over the place, either by crawling or riding on the backs of bees.

Just like ticks ride around on deer, squirrels, mice, whatever -- and also lurk in the bushes looking for somebody to glom onto.

BTW I ran years worth of experiments on screened bottom boards at the Dyce Lab and we never saw any effect whatsoever. I have always thought that the idea that mites fall off bees and can't get back up, is pure nonsense.

Michael Bush

· #8 · Aug 5, 2014

I suspect not that many fall off. I never saw any difference in Varroa from Screened Bottom Boards either. But I don't think that was the original question...

Robbin

· #9 · Aug 5, 2014

They can't crawl out of an oil tray back into a hive. I don't know if enough fall to make a big difference, but that oil tray kills a lot of SHB....

Seeing as we are on the subject of mites falling off bees, what makes them fall off when they are treated with OAV?

Phoebee

· #10 · Aug 5, 2014

What makes them fall off for any one of a number of reasons?

Story of two hives, both of which produce the same low mite counts during recent powdered sugar rolls.

Hive A has a drop rate of about 7-8 mites per week into an oil tray, and the last roll produced 2 mites, supposedly less than a 1% infestation.

Hive O had the same sugar roll rate as A, and a repeat last weekend produced 4 mites. However, the drop rate onto an IPM board has been steadily and dramatically increasing, to 174 mites last week (natural drop, didn't even sugar dust). The increase in drop rate started as soon as the queenless O was combined with a VSH nuc, whose brood is taking over the hive. So the question is, is this VSH breed doing something to drop mites (they supposedly will remove infested brood)? If this is an actual infestation, why are the sugar rolls producing such low rates? And while I'm cleaning the IPM board, I stick in a dry tray. The mites dropping into the tray are mostly live.

Somebody out there must have studied this mite dropping behavior. I expect there are a lot of factors involved, including mite population, but also grooming behavior. Africanized bees are supposedly better groomers. Is this also a trait of some VSH bees? I think the drop rate is an interesting observation but probably not great for hard counts. I'd hate to label a hive of good groomers as being prone to varroa infestation if, in fact, the very opposite is true. But I'd also hate to lose this presently very productive hive to varroa.

How effective a SBB is would have everything to do with what makes mites fall off of bees. For a natural drop rate, that could have everything to do with grooming, which could be very dependent on breed.

I may resort to an alcohol wash to get a really good count on Hive O.

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Slow Drone

· #11 · Aug 5, 2014

Female Varroa live 27 days when there is brood present in the hive, 2 to 3 months during the summer, up to 6 months in the winter.

peterloringborst

· #12 · Aug 5, 2014

How effective a SBB is would have everything to do with what makes mites fall off of bees.

No, how effective would depend on whether they crawl back or not. Obviously dead mites aren't crawling back up. If they are falling because they are already dead, that tells you very little.

In fact, I have studied mite drop extensively and it is very deceptive. You can get a heavy drop from a very large colony with a moderate level of mites, and the same drop from a moderate sized colony with a heavy mite load. Worse, you can get a very light drop from healthy colonies with few mites, and also from colonies about to die, where the mite infested bees have absconded.

I would never use mite drop as an indicator of mite infestation. Either alcohol wash or sugar roll are the correct tools.

Phoebee

· #13 · Aug 5, 2014

peterloringborst said:
No, how effective would depend on whether they crawl back or not. Obviously dead mites aren't crawling back up. If they are falling because they are already dead, that tells you very little.

Well, I'd say if they are dead when they fall off that's a pretty good reason why they fell off, but point taken.

Still, in fresh drop from this hive, I'm seeing live mites in the tray (which goes in while I count and clean the IPM board). So, at least for this hive, they're dropping a lot of live mites.

I'm also seeing a lot of lighter colors in the IPM drops. I need to get a batch of these under the microscope to see if they are really mites or just exoskeletons, or if some of them are not quite developed.

How do you study mite drop? I just got a small obs hive and one of my plans for it is to video bee-havior, including induced grooming by powdered sugar dusting.

peterloringborst

· #14 · Aug 5, 2014

Phoebee said:
Well, I'd say if they are dead when they fall off that's a pretty good reason why they fell off, but point taken.

What I meant was: you don't know if they died from old age or from some sort of behavior on the bee's part (or from some chemical, for that matter). The chief problem with mites, however, is reinfestation.

Mite populations can increase due to the drifting of foragers from infested colonies or robbing failing colonies infested with mites. The extent that immigration affects mite population growth in colonies is not known. Mite migration has been reported to occur from heavily infested colonies that were 1.5 km away.

DeGrandi-Hoffman, G., Ahumada, F., Curry, R., Probasco, G., & Schantz, L. (2014). Population growth of Varroa destructor (Acari: Varroidae) in commercial honey bee colonies treated with beta plant acids. Experimental and Applied Acarology, 1-16.

estreya

· #15 · Aug 6, 2014 (Edited)

Very interesting thread. I'm new to beekeeping this year, and unfortunately, i was in la-la-land and thought i wouldn't have to learn about mites until next year!

Pffft.

Did i just read on this thread that screened bottom boards do NOT offer a significant advantage in dealing with mite loads? This would be a relief to me since i've been beating myself up over having decided on solid bottoms. Having just performed our first sugar dusting (pictures are at http://wabeekeepersforum.proboards.com/thread/1796/photographs-inspection-varroa-edition-photo) it certainly seems as if screened bottoms would have made the process a little easier.

Andrew Dewey

· #16 · Aug 6, 2014

I use solid bottom boards too. It is reported that sbb make a slight difference in mite infestation - not enough to "deal" with mites as a stand alone solution.

estreya

· #17 · Aug 6, 2014

Thanks, Andrew. In another thread, Michael Bush recommended a sticky board from Dadant (http://www.dadant.com/catalog/product_info.php?products_id=352) that could be placed on the bottom of the hive in the absence of a screened bottom board. I ended up purchasing a set from Mann Lake that's basically the same thing (http://www.mannlakeltd.com/mm5/merc...nnlake&sType=1&Search=sticky+board#!DC-680/1/). It'll be interesting to see next weekend if anything stuck.

ruthiesbees

· #18 · Aug 7, 2014

Following this thread...I plan to do sugar rolls this weekend to measure the amount of mites in each of my hives. 2 have been queenless for about 3 weeks as they raise a new queen, so that should have an impact on the numbers. For the one hive that has had a queen the whole time, I might treat with powdered sugar to see how effective that is. (tried it on a nuc in July, but it succumbed to SHB a few weeks ago)

But I am also using a SBB with a solid IPM board underneath. On that IPM board, I have diatomaceous earth, which is doing a good job of killing the small hive beetles--adults and larvae. I would think it would also kill any varroa mites that fall through as DE is used on chickens for mites in their feathers.

Robbin

· #19 · Aug 7, 2014

estreya said:
Very interesting thread. I'm new to beekeeping this year, and unfortunately, i was in la-la-land and thought i wouldn't have to learn about mites until next year! Pffft.

Did i just read on this thread that screened bottom boards do NOT offer a significant advantage in dealing with mite loads? This would be a relief to me since i've been beating myself up over having decided on solid bottoms. Having just performed our first sugar dusting (pictures are at http://wabeekeepersforum.proboards.com/thread/1796/photographs-inspection-varroa-edition-photo) it certainly seems as if screened bottoms would have made the process a little easier.

I sat in a UF seminar and the PHD said a UF study showed 14% fewer mites with SBB. Not enough to defeat the little monsters, but a step in the right direction. I use both. I prefer SBB with Oil trays to kill SHB, but they are expensive. I use my solids because I bought them first. When I buy new, I buy SBB, usually with trays. I'm trying TF with Beeweaver queens and SBB.
My treated hives are OAV and that simply works great, for very little money. If I had 100 hives it might be too much work, but I don't . If I stay under 50, I'll probably stay with OAV.
Trying beetle barns this year and some of the beetle paper that supposed to catch them. We'll see.

peterloringborst

· #20 · Aug 7, 2014

Did i just read on this thread that screened bottom boards do NOT offer a significant advantage in dealing with mite loads?

No significant advantage.

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