I am confident that those are mites. I have seen both mites and mosaic virus on Bambusa plants. The "webbing" really looks to me like a very thin layer of plastic covering the colony. Use a hand lens, and look at the back of every leaf until you find a colony with the webbing intact. This...

Google bamboo mite damage and see what you think, it looks pretty spot on to me. No pun intended... Hmmm, yes it does, although some pictures of BaMV look like that as well. I would have expected the underside of a mite infested leaf to have more of that webbing/tenting stuff on the back. These lea...

Any idea what ails my bamboos? Could this be the dreaded BamV?
It has gotten to my Oldhamii (pictured), Vittata, Wamin, and now perhaps my Dendro Minor Amoenus.