Thanks, Father'sDaughter, that's a great link... You can't beat simple, straightforward treatments that a grower has used and found helpful and not harmful. Reading about this is making me really mindful of the compost issues for disposing any commercial garlic - I still had to buy some this year - which could bring along any number of pests or diseases.
The alcohol dip for mites is a great idea. (vodka ?
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The good news about garlic viruses, they don't seem to be easily transmitted although the diseased plant material should be burnt not composted. The worst one is called Onion Yellow Dwarf virus - it can be spread by insects that puncture the leaves but doesn't spread by simple contact afaict, and it isn't soil borne, but will overwinter on volunteers or perennial onions. I had a walk around the garden this morning and there's no sign of any symptom on my several patches of leeks, three kinds of green onions, chives, bulbing onions.... thank goodness. So I guess that isn't the problem.
The rounds that seem to be affected are from the same two varieties - Chesnok Red and Leningrad - and some Persian Stars that were grown in the same small tub. So it may have been latent on one or both of these and the spread wasn't too far. Or possibly what I'm seeing is just insect damage and not the same thing - hard to tell on the smaller foliage, which is also drying down really fast. I still need to read more about mosaic virus on garlic, but for now I think I would go ahead and plant these big rounds in a separate place away from the others, and just keep a very close watch on them next season and pull and dispose if there's any sign of virus. Unless there is something more contagious about mosaic than the other.
The worst effect of latent virus seems to be, it can reduce the size of your bulbs. So ultimately the practice of replanting the biggest ones would also help to weed out virus or susceptibility to it or its negative effects. I certainly won't be replanting any of those tiny cloves.
The rounds were a good size, so I'm not seeing this concern. I don't understand why growing stock from bulbils restores the vigour of the stock so they say, but maybe it will...
I do think the small size of the Chesnok bulbs can be mostly blamed on the weather and the lateness of these purple stripe varieties - they're just not as well adapted to our short season and cool conditions in the first place.
Most of my bulbils last year were from Persian Star, and it's a late one as well... Not a great choice I guess.
So for sure, this time I'm going to focus on planting some bulbils from the healthy Music and Argentina, and try to increase my seed stock of varieties that really do better here.