Too much light?

[estación seca]

Systemics get into the vascular tissues of plants - the veins - but not so much into the cells themselves. Chewing insects will eat veins, ingest the poison and die. Mites being so small stick their proboscidea into individual cells or groups of cells, not veins, so they are not much exposed to systemics.

Imidacloprid applied to a mite's body will kill it, but systemic imidacloprid is not effective for mites.

No Dens should dry out when they are pushing active growth. I'm more and more convinced most people lose Dens because they don't water enough when new growth is forming. The Aussie Dens descend from ancestors with a much drier winter, when they are not pushing growth. But if it is making new growth, water heavily.

[Cym Ladye]

This does not look like any mite damage I have ever seen. I would look further into one of the viruses but if it is a small plant, I would toss it. I would send a photo to Sunset and ask his opinion. He is very reputable.

[SundayGardener]

That's a good idea. I will contact him. I'm embarrassed though... a bad tender of his orchids If nothing else, I'm wondering if I should remove the leaves, or the entire cane.

It's separated from the other dendrobiums at this point. I've seen a few dodgy leaves on them too but I'm watching them.

Not to sound like a complete idiot, but isn't it time yet to lay off the heavy watering? It's mid-October! It's cold! We saw snow yesterday! These dens aren't going to lose their leaves, so what I'm asking is how do I know when to back off? I've got one that just keeps on producing new shoots.

On the other hand, I've got an unexpected bud on a cattleya so they seem to have their own ideas about timing.

[Dollythehun]

If you see active growth, I personally, would keep watering.

[estación seca]

You water heavily from the time (usually spring) you see new growth eyes elongating at the bases, and new roots forming, until all the new growths are mature and finished growing. Then you cut back.