Thanks,

Don't think it is insect, because if I look at it through a magnifying
glass, it looks more like a pitting of the leaves, than anything actually on
them. Tips and edges then turn brown, and then it is a matter of time. Due
to space considerations they were packed together, so in hindsight I can
understand that whatever it is would spread.

Thanks to all for responding.

"Steve" wrote in message
...
eeyore wrote:
Hello,

Sorry I can't post photos, but I'm wondering if anyone could identify
what would cause a white, almost powdery look, on the top of the leaves.
This leads to yellow leaves or black blotches on the leaves and then a
dropping of all the leaves. Roots look fine, but not sure what chance I
have with nothing but roots.

Started with my phal's but is expanding to all varieties. Very hot
summer here so at first I assumed it was sunburn, but since it continues
into the fall, it has to be something else.

Hope someone can help, I'm not a scientific grower, just been having
a lot of fun buying orchids that have dropped their blooms for a cheap
price, and getting them to rebloom. I was doing great, until whatever
this is took over.

Thanks!

Are you familiar enough with boisduval scale to rule that out? I'm pretty
sure that what you are describing is a much thinner layer than a what a
colony of scale would be. Still, if you didn't realize what you were
seeing and let it go, it sure can yellow the leaves and kill plants.
I searched the internet for a picture and the one on Ray's site was better
than most so I'll show that one: http://www.firstrays.com/scale.htm

Steve