How are "survivor/hygenic" bees resistant ot Varroa?

[windfall]

I am having a hard time finding good info on the mechanism by which resistant stocks are resistant. I have seen some reference to hair types and speed of development...I believe this implies greater difficulty in the mites attaching? I have seen more reference to increased grooming, I assume this means the bees are removing more attached mites? I guess the question I am asking is what sort of physiological/morphological traits and/or behavioral traits are aiding these bees?

The question first jumped at me as I was considering screen bottom boards or not....If the bees are removing the mites, are they killing them or just dropping them? If the latter it seems that a screen bottom becomes much more important in getting the maximum advantage of the bees behavior. However, if they are killing the mites first...they are just that much more inert debris.

[Robo]

I don't have an answer for you, but I don't believe it is a grooming only trait.  I believe it also has to do with the bees ability to detect mites on the larvae and tearing them out before they can reproduce.

Also keep in mind, that there are mixed results on SBB and mites.  Besides the ones that believe it allows for dislodged mites to fall to the ground and not return to the nest,  there are also those that believe a SBB makes the brood area cooler and drier.  Two conditions that favor mite reproduction.   So you decide  :?


BTW, I have never seen a feral survivor nest with a SBB. :-D   All the ones I have seen make every attempt to seal up the cavity to retain heat and perhaps scent.

[windfall]

I do try to bear in mind the mixed results on SBB. I read the studies you cited in an old thread regarding temps, and try to weigh them against the studies showing a statistically significant drop rate removed from the hive by SBB. It is probably a marginal difference in the end...if it were really having a substantial impact either way the debate would resolve pretty quick.
I have seen you bring up the issue of retaining hive heat in a number of threads; supported by you observations on feral hives and how they seem to choose cavities that are sealable and proceed to do so (seal them up). It makes a great deal of intuitive sense to me that the bees will do better when they control the air flow through the hive. It has frustrated me in the old threads that no one seems to engage/discuss this point with you...(I think I know where your stance is on venting now, but sometimes I get the chronology of old posts mixed up)
Obviously there is another strong and respected camp for increased and top ventilation; and it's hard to argue with some of the the good results many of them are having. Sorting it all out is tough on newbie!

But I lean toward a closed hive. It seems if you are only maintaining a few hives around your property it would not be much of a chore to keep a good sealed tray under a SBB and routinely clean it out. Which would perhaps allow for some benefit from mite drop random and/or hygenic...take any benefit you can?

[Robo]

Yes, a closed SBB does take the best of both arguments. The only draw back it creates an ideal environment for wax moth between the screen and tray.  The screen protects them from the bees while still allowing food to fall through.  It is not a big deal for strong colonies.  But if a colony gets weak, the wax moth can over power it. 

It mainly comes down to the decision on whether the added cost is worth it.  When I was getting away from SBB, that is exactly what I did.  In fact I still occasionally use them in this fashion when I'm running short on equipment.

I've also been experimenting with a different kind of bottom board that leaves a large open space below the frames, and does not use #8 hardware cloth.  I do see varroa on the tray,  and I have no idea if any of the fallen ones can crawl back up the sides to the comb.  But it does eliminate the issues with wax moths and it also eliminates varroa on the bottom board latching on to incoming bees.  The bees enter the hive vertically and up the inside of the hive body.   

My thought were not based upon varroa, but think it may apply to your questions.   My objectives where to give space for the bees to cluster both under the frames and under the entrance out of the weather. The entrance is small enough to act as a mouse guard,  and the wind and nasty weather can't blow directly into the hive.  It also does not need any reducer for the winter.  So far I have been happy with them.  The only drawback that I can think of, is if the bees get crowded, they may draw comb down from the bottom of the frames.  I have not had any issues with that yet, but then again, I make sure they have plenty of room above the brood nest and my location is not ideal for copious amounts of comb building anyway.  If comb building becomes an issue,  a piece of florescent light diffuser could be used to limit the brood nest and still provide access for the bees to keep wax moths at bay.

[rdy-b]

  In my mind they are not resistant to varoa-rather survivor stock has a genetic propensity
to be resist and overcome the VIRUSES that the mites vector-there are many bee lines that can handle
high mite loads-viruses and pathogen resistance is the key-good grooming and screen bottom boards
just help reduce the mite load--RDY-B

[windfall]

rdy-b,
That's an interesting take I had not considered. While I was aware that the mites acted as vector for a number of viruses, I had assumed the primary mechanism of damage was the parasitic overload from the mites themselves. This gets into some interesting stuff I used to study regarding virus (or any parasite) virulence. Essentialy, a parasitic organism c an only become destructively/fatally virulent when natural populations are in exponential growth, or in the case of bees artificially sustained.but that is a whole different topic.

robo,
that bottom board is quite interesting. I had been sketching up some exterior entrance modifications that create a weather baffle like it does. The few feral hives I have seen in buildings took advantage of that effect. How long have you been employing them? how many have you tried? I like the idea of a space below the hive...I have seen some folks doing warre refer to it as a "sump", it would seem to mimic more closely a vertical tree cavity. I never hear folks doing cutouts talking about bees walking across the "bottoms" of the hive.
Cost really isn't an issue at the scale I am working. Woodwork is my trade so I build everything myself in downtime from scrap. for me the actual cash outlay is in buying bees...these local treatment free nucs are not cheap! Which is not to say I think they are overpriced. So my motivation is in providing a optimal space for them to grow in.

[Countryboy]

Are you talking about survivor colonies in managed hives, or survivor colonies in feral hives?

One of the ways feral colonies stay alive is by selecting cavities that are about the size of a single deep.  The colony is not able to grow very large before it swarms, which breaks the mite brood cycle.

[windfall]

I was referring to bees being bred as treatment free for management. But I do understand that even with these a well timed break in brood cycle can be of great benefit.

[rdy-b]

mites dont kill the bees its the viruses they vector-and the viruses are always mutating
much like the flu dose -we already know how mites reproduce they mate with the first male mite that was laid before cell was caped-that mite is the brother of the female mite-this keeps the progeny line of the mite (as well as the genetic propensity of virus strain ) -in check-But if there is a over population of mites it is possible and dose happen that there are TWO males laid in the cell from different mothers -two male mites in a cell are not uncommon-so now the mites are breeding outside there sustained lineage-and now we have mite genetics coming into play -and we have new viruses created just like the flu bug-if this happens to a large extent there can be a cascade affect and the new virus load that is created with the new virus-crashes the colony
:) RDY-B

[Michael Bush]

>I am having a hard time finding good info on the mechanism by which resistant stocks are resistant. I have seen some reference to hair types and speed of development...I believe this implies greater difficulty in the mites attaching?

Reality is very complex.  There is probably not one mechanism involved. In my opinion, as far as Varroa is concerned, it's just cell size.  As far as wintering, it's all genetics, as far as Tracheal mites, it's genetics.  As far as other brood diseases, it's hard to say.  But small cell people have noted more biting of mites and more hygienic behavior.  But this would not be genetics.  Shorter capping and post capping times.  But again, I don't think this is genetic.  The traits that the scientists have been breeding for are mostly hygienic behavior.  But I'm not convinced that it's one trait.

> I have seen more reference to increased grooming, I assume this means the bees are removing more attached mites?

That would be the definition.

>The question first jumped at me as I was considering screen bottom boards or not....If the bees are removing the mites, are they killing them or just dropping them?

Small cell beekeepers have noted and taken pictures of mites that are dented from biting and some have gotten videos of bees biting mites.

[Brian D. Bray]

IMHO, survivor/hygenic bees have all of the following traits to some degree.

1. Grooming (includes biting of mites)
2. Brood interruption cycles
3. use of smaller cell radius
4. Reopening of infected cells and removal of larva
5. period kill off of drones (several times during season)

There may be others but those are the ones I've identified so far.

[backyard warrior]

Country boy you have lots of good info and are knowledgeable like many others here i hope you stick around.