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Discussion Starter · #1 ·
I put robbing screens on in September on many of my solid bottom board hives. They were all thriving. I discovered today that most of those hives have a ton of dead bees at the entrance and the hives are lost. There is plenty of honey in the hives and they were treated with OA in August 3 straight weeks and throughout the summer as well. There is a quarter inch hole drilled up top for upper ventilation. Did the robbing screen cause the issue? The base of the robbing screen doe not sit flush up against the entrance, there is a half an inch or more space from the entrance along the width of the bottom board.
 

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Loads of dead bees on the bottom board this time of year usually suggests starvation or heavy varroa infestation, in my experience.
I’m sure I’ll take a lot of abuse from the oav crowd for saying this but I haven’t had dependable results with oav during brood rearing season….regardless of the protocol I used.
In Gatlinburg, TN this time of year I don’t think it was robbing.
 

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Aylett, VA 10-frame double deep Langstroth
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Two things come to mind for me. You treated in August with OAV. What about the follow up treatments in Sept, Oct, and November? OAV is not a one treatmet regimen and done form of mite control. Especially if done when there is still brood in the comb. In my opinion, there is a need to do follow up treatments no matter which treatment you use initially. As long as the bees are flying, there are mites coming into your hives.

Second, I notice you do not also have a bottom opening on your robber screen, at least I couldn't see it. With only a top entrance, the morgue bees must carry the dead ones up the screen and out, a time and labor intensive task as they drop their cargo often. That can lead to a clogged up landing board, but in this case had nothing to do with the death of your hive
 

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It sounds to me like the OP treated 3 times in Aug a week apart.

Alex
 

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Exactly, one treatment regimen or series, and in late summer. No mention of fall treatments.
 

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Discussion Starter · #8 ·
These were package bees that I treated in the package before installation. I treated them two more times before supering. Then the 3 in August and a final in mid- September. I did not test for mites at any time, but also have some screened bottoms with sticky boards that I checked a day later to see the mite drop after treatment, and all appeared ok.

I do not have a bottom opening on the robbing screen, but on the few I really examined, there was room to get out, and they were leaving and entering in Mid-December.

I have lost hives over the course of doing this, but I have never seen the hive dead on the bottom at the entrance. For me, it seems most of my losses due to mites (1)there is a dwindling and by the time winter hits, too small a cluster to survive, or (2) an absconding, or (3) too weak to defend fall robbers.

I may still be too naive on mites, but I thought I hit them pretty good. I did want to treat one more time in October/November, but did not.

I will check some of my other hives today.
 

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I am not going to speculate anything but I will tell you my observation when I used robber screen one winter. The entrances were clogged for some hives and there was moisture buildup in those hives. None of them died because I noticed the clog in early February and we have mild winters down south. But I learned my lesson to remove the robber screens before winter so they can keep the hive tidy by hauling dead bees in warm days during winter (and we have plenty of warm days now a days).

I have started to use robber screen selectively only on the hives that I am feeding and while I am feeding. I take them off after feeding is done. I know some weak hives can get robbed with this method but I would rather lose one/two weak hives than risk all of them.
 

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i have similarly constructed robber screens on a couple of my hives for the first time this year. i have been taken them off and raking out the dead bees on more or less a weekly basis. so far the entrances into the hives have not become completely blocked as shown in your photo, but i can see how they could become that way if i wasn't cleaning out the dead bees.

i'm thinking that the quarter inch hole for an upper vent may not be enough. you did not mention having any insulation at the top of the hive. if there wasn't any insulation up top i can picture how the clogged bottom entrance and too small of an upper vent could lead to cold condensation forming on the 'ceiling' inside the hive and dripping back down on the bees.
 

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Discussion Starter · #12 ·
Up top, it is a shim with a hole drilled in it. I put a sugar block on the top that generally covered about 3/4 of 3 or four frames in the middle. Our winter has been mild so far.
 

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Have you opened any of these hives to do an inside inspection?
That might give you a good idea of how they perished. If you do, please take pictures and share here.
 

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if it's cold enough for your breath to fog on your windshield then it's cold enough for condensation to form on the ceiling of the hive, especially if there is no insulation up top.

colonies in hollow trees don't have this issue. it's a real problem in the artificial 'trees' we place them into and why imo there needs to be insulation up there.
 

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It is possible to have a hive die from varroa even if the mite drop in Sept is 0 (and be sure to check 2 days after treatment, not less than 1 - mite fall is heaviest after 24 hrs, and continues moderately heavy for 7 d after, good that you were checking the bottom board). A hive that goes robbing can bring back enough mites to kill it. A hive that gets poor lost bee souls whose hive is crashing can also get enough mites to kill it. Not theory - observation, first hand experience.

Youe can confirm or deny the role of mites in a deadout by doing an alcohol wash on the dead bees. You'll want a mesh screen to hold the bees in and let the mites through, lots of good sites for making a "shaker", I use this one: http://scientificbeekeeping.com/mite-washer-still-improving/ . If you find more than 10 mites in a 1/2 c of bees (which is 300), then mites played a role.

If you want to know whether the mites were home-grown or imported, then you need to check for mite frass - tiny white deposits left by a mite after reproducing, on the front roof of the cell. Not mixed in with hive debris on the bottom of the cell. If you can see some, then that's too much - the mites were home grown. If not, then they were imported. Take pics with a well-lit, upside-down comb for your records...
 

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Discussion Starter · #16 ·
Mites appear to be an issue based on the comments above, all of which are appreciated. However, there are two other variables. One yard that mainly has solid bottoms with robbing screens is nearly lost, with the losses showing bees all over the bottom board. Another is ok, with most of the screened bottoms and no robbing screens making it. A third location with all solid bottoms with robbing screens is in much better shape than the first.

The yard that has the losses also has a bad history with robbers, so maybe mite infested bees make their way in the hives even with the screens?

Over 50 percent were packages, that were treated as I posted above. I even used the real OA from brushy mountain. My bad for not treating in October and November, lesson learned. It is still hard to believe package bees with no mites can be lost in 9 months as a result of mites especially when I treated as described (realizing two more may have helped).
 

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a robbing screen makes it more difficult for your hive to get robbed, and may help prevent your colony (if it crashes from mites) from spreading mites to other nearby colonies.

your bees can become mite infested if they go out and rob out an (unprotected with a robbing screen) hive crashing from mites, because the mites from the crashing hive jump on your bees and hitchhike back home with them.

your robbing screen doesn't help this. mite crashes and robbing are most common at the very end of the season, especially after whatever fall nectar flow you may have is over.
 

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the shotgun brood pattern in your photos is typical with mite collapse.

you can use a tweezers to uncap and remove the pupae. if you find them with deformed wings, stunted abdomens, or other deformities you will know there was a high viral load vectored by mites.
 

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It looks like you have a lot of mite frass on the cell walls if I am seeing correctly. Those are the white specs. So I would suspect a mite crash and rule out the robber screens having anything to do with the crash. Even though you did treat, I think your timing was off, and this is common going into fall thinking that you treated so everything will be ok. Reading here on the forum, it has become pretty obvious that our bees are very susceptible late summer and into the fall even if you treated. You(we) really need to know the mite load after we treat. Doing washes is the best way, but if you cant doing one shot of OAV and seeing the drops will give you a clue. But you have to keep doing the one shot until they are not flying here in the northeast. In Tenn you have to be more vigilant. J
 

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In picture #1, there seems to be a lot of bees head in cells. Are those bees alive and that hive is being robbed or are those bees dead?

I'm guessing all four pictures are not from the same hive.

Alex
 
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