Interesting Mite Reproduction Success

[Crofter]

http://bees.msu.edu/2012/varroa-repro/

This is one of the most thorough yet understandable articles on mite reproduction variables. AHB vs EHB  vs Apis Ceranae. Also goes into significance of different mite species.

[LazyBkpr]

Wow, Good read!
   This sheds a LOT of light on why certain methods and bees can produce "resistant" bees in one location that fail completely in another location.  The humidity factor being one of those things. If you have high humidity, resistant bees, and use some IPM you have a better chance of getting bees to survive than if you have low humidity;

 They artificially transferred single mites into newly capped cells, and then kept the brood in an incubator. When relative humidity (RH) was set at 59–68%, on average, 53% of the mites produced offspring (N=174 mites); under 79–85% RH, only 2% (N = 127) of the mites reproduced. The difference in mite fertility was highly significant. My postdoctor recently incorrectly set the incubator at a RH of 75% (instead of 50%), and very few mites reproduced as a result. If there are ways to artificially increase the hive RH to about 80%, then the varroa mite population will never increase to a damaging level.

   I also did not realize that the bees only targeted and removed Pupae that had female mites;

 the bees do not open cells containing non-reproducing mites, but rather target those having mite daughters.

   And of course the ever popular small cell debate. I had read this before;

 An earlier study (Message and Goncalves, 1995) showed in Africanized bees, larger cells had a higher invasion rate, and also had higher effective fecundity in mites.

   And in this statement he seems to contradict himself, saying that Mites Increase in smaller cells, yet closer to the bottom he seems to indicate otherwise..   so not sure how to interpret it?

we accidentally discovered that in both A. cerana and A. mellifera queens laid worker eggs in drone cells in the fall.  We took advantage of this, and compared the reproductive output of mites on two hosts: workers reared in worker-cells (WW) or workers reared in drone-cells (WD).   In 2001, both the fertility and fecundity of the two groups were significantly different (Fig. 4). It is not clear why mites would reproduce less on identical hosts that were housed in larger cells. One possibility is that workers reared in drone cells are fed a different diet by nurses (One study showed workers reared in drone cells were heavier and had more ovaries, suggesting a different diet or more nutrition).  A second possibility is that workers spin larger cocoons in drone cells, and mites detect the extra space, and this affects their reproduction.

  LOL, so which is it? Less or more?

   Good read. Thanks for posting the Link!

[Crofter]

On the divergent answers to cell size I think it might point to there often being other, stronger forces at play that were unaccounted for by the various experiments. If cell size were a cut and dried controlling factor in mite suppression the matter would have been settled long ago.

[LazyBkpr]

On the divergent answers to cell size I think it might point to there often being other, stronger forces at play that were unaccounted for by the various experiments. If cell size were a cut and dried controlling factor in mite suppression the matter would have been settled long ago.

   Very true..
   Another thought;

 (One study showed workers reared in drone cells were heavier and had more ovaries, suggesting a different diet or more nutrition)

   Would that also translate to a greater ease of developing a laying worker?

[Crofter]

That would seem a natural consequence. Make them more dastardly if they were to lay anyways!

[Crofter]

I dont know whether in that link or another recent read that allowing a hive to die from mites in an apiary (and subsequently get robbed) tends to select for more virulent mites that kill their host. The same pressure on a remote feral hive would tend to terminate their genetics. What works in nature at natural distribution levels, works against them when crowded. Now the idea that allowing a certain level of mites to trigger defensive mechanisms, sounds logical too. So many times the argument goes back and forth depending on what hunch a person decided to go with and build their thought processes upon.  I despair! It is so darned hard to control the variables when you dont even know what they all are!

[LazyBkpr]

 I despair! It is so darned hard to control the variables when you dont even know what they all are!

   And so we become of one mind!

[tecumseh]

there is an article which I have only had the opportunity to speed read in Bee Culture concerning what is known about small cell vs standard cell and it's impact/non impact on varroa population.  I do not subscribe to Bee Culture.  I seem to recall the author was Ross Conrad.

[LazyBkpr]

Topic for discussion...
  In talking with a couple other beeks last night after the meeting...  ONE of them said...

   "I use natural cell because the bees can make the drones they want. The mites are naturally drawn to the drone cells.. So in effect, its the DRONES that get most of the damage from them, not the workers."

   Somehow, in a wierd sort of way.. that made sense to me..   maybe it was because we had the meeting at a bar?

[iddee]

Sounds like he wants to ensure he raises enough mites to do the hive in.

[Gypsi]

The humidity factor in mite reproduction could become very important to me, as our relative humidity around here has been less than 50% for months. I had more mites on my VSH bees than every before last fall.  I have ordered new vsh queens. I powdered sugared the hives just before first frost and I do use SBB's with a sticky.  Haven't seen a lot of mites on the stickies this winter, couple of small hive beetles and a lot of robbed wax when the robbing got going.