I'm guessing this is brown bacterial rot which means the plant may die within weeks. I got this in the mail yesterday with only a few of these spots but now a big one has formed on this leaf. So far I've wiped all the leaves with full strength listerine. I'm going to get some physan 20 very soon with my next order. Is there any other way I can stop the rot from spreading?
I usually remove the infected part of the leaf and treat the rest of the leaves and stem with Isopropyl alcohol (be careful not to get it on the roots or any buds/spikes). The lysterine should be fine, too. I find that adding some extra calcium seems to help prevent issues with my Angraecoids. I think it has something to do with building stronger cell walls...I cannot remember the details exactly. Many people just use preventive fungicides on the Angraecoids because they are known for having issues. I haven't done this but I have learned to keep the water off of the leaves when the temperatures are cooler.
Also, with the Angraecoids, be careful to flush the pot or mount periodically to get rid of excess salts. They are sensitive to water quality (but are usually okay if you flush them well and go light on the fertilizer).
If it's bacterial rot, the bacteria aren't present beyond the margin of the brown mark. But they are all over the brown partm, and anything that touches the brown part can get contaminated, ready to transmit the bacteria to something else. So, you need to treat it as infectious.
Scrub your hands with soap and water. Cut off the leaf below the brown mark and put it straight into the trash. Sterilize your blade afterward by heating in the oven or exposing to alcohol for 20 minutes. Scrub your hands again. Treat the plant if you wish, but with good cultivation the bacteria should not attack.
__________________ May the bridges I've burned light my way.
Well, good luck with it. I know, here, the temperatures can turn cold/hot without warning (defying the forecast). I ordered a Lepanthes telipogoniflora (along with some other orchids) from Andy's when the temperatures should have been good for shipping and we had an unexpected hot day and it is still trying to recover.