Sol, more and less virulent mites are not hypothetical, in your country, they are fact. You have mites of several different known strains, and the japonica one is regarded as less virulent. Highly likely there are also several sub strains that have not even been identified.
In my country, we only have the one strain, unfortunately, the most virulent. Also interesting that nobody in my country is treatment free, in the fullest sense of the word, and had them survive more than 2 years.
Regarding the bee drift idea, it may be important during robbing etc. But the primary way mites spread is at flowers. This is not always easily seen as one bee may visit hundreds / thousands flowers. But large enough varroa mite numbers to be easily seen have been reported on your own US cotton crops.
And yes, I know cotton is wind pollinated. But bees will happily pollinate it also.
HPM08.... I believe he used the right terminology, strain. All of the mites are of the same species, because they can interbreed. A Human parallel would be blonds, red heads and brunets(sp?). They may all be Human, but we all know it is not wise to anger the Red heads.
Crazy Roland, son of a Red Head.
I'd go with Roland, in this instance I think strain would be the correct word. Not an expert though. I guess it's like bees. Would italian, caucasion, and african bees be different strains, or different species? I guess it would be strains.
Yes it would be useful to ID the mites involved in not only studies, but also if the less virulent ones are in fact the ones infesting the hives that are coexisting with them, ie, the "successful" treatment free people.
Yet another variable for researchers to worry about!
If we could isolate and propogate less virulent strains of Varroa mites could we put them in our hives? Do more virulent strain mites displace the less virulent strain mites?
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I've read that only one strain will inhabit a hive, that seems to be the common wisdom, but I suspect it is might just be chat site banter.
To me, it doesn't really add up you can only have one. What happens if a mite of a different strain arrived in a hive. The other ones would kill it? Doubt it.
I've searched (in the past), but have not been able to find a proper study on it, and not sure if ones been done, so maybe nobody really knows for sure.
Has it been established, that different strains have different levels of virulence?
No it's heresay. However there is anecdotal evidence for it, just hasn't been proved in a study.
Sounds like it is also anecdotal that hives are infest by one strain of mite at a time. Perhaps that would be an easy one for some researcher to tackle first.
All in all... it seems like there are a lot areas that have been discussed here that are ripe for research or additional research. Wonder if anyone has anything currently going on. Seems like there would have to be.
>Do more virulent strain mites displace the less virulent strain mites?
The more virulent strains would be the ones the reproduce more... meaning the only apparent mechanism for less virulent strains to out survive them is by NOT killing their host while the virulent ones kill their host, meaning it is only by the colony dying that you breed out the virulent ones.
Michael are you sure of that, or is it just something that appeared logical?
When I had to study up two particular strains, one more benign than the other, I didn't see anything about different rates of reproduction.
The concept is proven in epidemiology. Look up syphilis and how it affected humans 500 years ago vs how it affects us today. The strains around today are definitely less virulent. The only explanation of the difference is that the more virulent strains killed their host which ended their ability to reproduce.
DarJones - 45 years, 10 colonies (max 40), sideliner, treatment free since 2005, 11 frame broodnest, small cell
Hi Fusion Power, for sure, I’m aware and agree with what you say.
However this is not quite what I was asking Michael.
In evolutionary theory, a less virulent pathogen that allows it’s host better health, will be likely to do better itself.
However this does not have to exclude other mechanisms for virulence, or confine them solely to rate of reproduction.
Really I’m just picking Michaels brains, maybe he knows something about this I don’t, if so, I’d like to hear it.
I based the assumption on my experience with Varroa, which is that the reason for the demise of the colony appears to be the rate of reproduction. So it seems "virulence" would be the mites that reproduce at a rate to survive the treatments and still outbreed any of the other mites. Which is why I've been saying for years that treating is the path to super mites and wimpy bees. You breed mites that can reproduce enough to survive the treatments and bees that cannot withstand the mites. What else would "virulence" be in this scenario? I doubt that one would eat more hemelymph or pass any more or less viruses.
Thanks, and I don't know what other mechanisms might cause more or less virulence. I was just seeing what you based your statement on, I'm always seeing if I can learn something.
Fascinating turn taken in this discussion now, I think. Before we get too far down the road, I'd like to clarify a couple things.
First, the "strains" of mites being discussed here are really subspecies (based on the naming conventions). "Races" or "subspecies" can be used somewhat interchangeably. Just like honey bee subspecies, mite subspecies can interbreed, and show some evidence of separation along the lines of a continuum. You can recognize differences between a "pure" representative of one subspecies and a "pure" representative of a second subspecies, but you may not be able to identify every individual to the subspecific level definitively.
And, once they interbreed, how do you recognize one from another? Think of it in terms of honey bees: you cross Italian bees with Carniolan bees. The resulting bees belong to which subspecies?
So, assuming that Varroa interbreed freely within a hive, each hive would end up with a single gene pool of mites. If something prevents that interbreeding, and if selective pressures foster isolation of different forms within a hive, you could end up with different subspecies or strains of mites in a single hive.
Next, with regards to virulence, the term that I should have used in earlier posts was "viruliferous." Viruliferous mites are ones carrying viruses. Even a very low population of viruliferous mites in a hive could pose a far greater threat to that hive than a larger population of aviruliferous mites.
How do varroa interbreed? My understanding is that they are, in effect, inbred.
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If only one Varroa enters the cell before capping they are inbred. If two or more Varroa enter the cell before capping and those Varroa are not full sisters, then you get interbreeding.