Question
I have had a couple phalaenopsis orchids together near a window
sill for about a year now. They seem happy and are flowering. When
I went to water them this morning I noticed that one of the large
mature leaves on one of the orchids looked as if it was liquifying
from the end. The end was very limp and almost disintegrating.
The rest of the leaf to the base seems fine. It seemed that this "rot"
was spreading from the outside in. I can't find anything in my
books about what this is or what is causing it. Can you give me any
information about what this is and what I should do about it?

Answer
Hello Marcy,

While I can't be certain without seeing it, the symptom you describe sounds like it may be a bacterial infection. My advice would be to remove the entire leaf all the way to the base. Be sure to use a sterile cutter and do not reuse the cutter unless it has been sterilized thorougly. If any of the liquidy stuff has dropped on other leaves, you may want to cut off those too with a sterile cutter. I use industrial grade single-edged razor blades for this purpose, just throw it away after use. Most paint stores have these blades as they are used on paint scrapers and are relatively cheap.

Doing the above may make the phalaenopsis plant look wierd but this may save it - I hope. If it survives, new leafs should slowly grow and in a year or two they will replace the ones you did surgery upon.  

Hope this helps.  Good luck and good growing.

Jim Kawasaki
San Jose, Ca.