Hi all:
What is this on my dend leaves? I have wiped it with alcohol and hydrogen peroxide and soap solution, but it is still there. Any thoughts...

Without being able to see and touch the leaf, this is difficult but I will give you my best guess. The line patterns on the upper leaf look like a mosaic virus. Just which one is hard to say. If it is reddish in color, it is probably tobacco mosaic virus. The white power like substance on the lower leaf looks like salt residue, perhaps from hard water or fertilizer? The two black spots on the lower leaf could be Cercospora Leaf Spot. Is the under side of the spot yellow? This is a common fungus on Dendrobiums.

Jim

I used a mild wash of diluted mayonnaise to remove the salt deposits on my den leaves. The acid from the vinegar dissolves the deposits, and the oil in the mayo leaves a nice shine. I got this advice from a grower at an orchid show when I asked him how he got the leaves so nice and shiny.

Just dilute about a tsp. of mayo with a couple of tsp. water and mix well. Dip a paper towel in it, and rub on the leaves. Rinse any off with another damp paper towel and dry.

Is the grid pattern on the top right leaf from sunlight shining through screening?

Ha, I had that sunburn through screening thought too but wondered why it would only show up on part of the leaf.

Jim