2-15-04
I am revising this page with a combination of some of the original pictures and some new ones. I hope to better show how the disease progresses. When I first put this page together, only 2 plants had actually died. Now, several months later, about 8 have died and several others are weeks to months away from death. At this point, I would destroy the whole group except for the sentimental value of one of the plants. That one is the first orchid I ever owned and there is a certain amount of pride that I kept it alive all these years. I'm still wishing there could be a cure.
Phals were so easy. They grew and flowered with no problem. In the late 1980s I decided I needed more Phals. I purchased some small seedlings increasing my Phal collection to 20. These grew up to be nice healthy flowering plants. Though it would be easy to find ways to improve my growing conditions, the conditions were (and still are) good enough to grow healthy Phals. Then THE DISEASE hit. Much of the following text is what I wrote originally with revisions where needed.


I am not new to growing these plants. All are several years old and one of these Phals is the first orchid I ever owned, dating back to about 1975.  These are window sill plants. My other orchids spend most of their time in the basement under HID lights. This group of 20 Phals stay upstairs where it stays slightly warmer. I have been growing Phals in this location for just about 25 years  and the conditions have not changed. For all of these years they remained healthy and close to spot free until July of 2002 when something changed.

That July, during a hot dry spell, about 5 of the plants got patches of  dark pits on one leaf. Usually it was the newest mature leaf, not the older leaves and not on a new leaf that was still growing. Within 2 weeks, more leaves were involved and another 5 plants were showing symptoms.  The first 5 plants were all adjacent to each other. The next 5 to get involved were all together and  just to the side of the first ones. Obviously this was a problem that could spread from plant to plant. 

The disease never affects the newly growing leaf. It starts in the youngest mature leaf then works its way down to the lower leaves. As the plant declines, it stops growing new leaves and finally it becomes leafless. At this point the roots are still alive and often completely healthy. The plant usually sprouts out one, two or sometimes three shoots from the base. These grow well until about the 2nd leaf stage when the disease starts again.

Things I have considered and treatments I have tried:

Mites?
This was my first thought because it was the pitting of the leaves that I first noticed. I thought maybe some type of false spider mite since both upper and lower surfaces get pitted. The first treatment I tried was sun oil. I sprayed 5 times at about 7 day intervals. I sprayed the oil and covered every exposed surface. The leaves had an oily feel and should have been very hostile to any mite. Nothing, either good or bad, happened.
There is no evidence of mites. Tapping the leaves over a white sheet of paper causes nothing to fall to the paper. Dragging a white piece of paper over the affected leaves does not leave any tiny streaks from smashed mites.

Virus?
There is no virus that spreads like this.  The plants  don't  touch each other. I have known for decades to use sterile cutting tools if  tools are needed. There are no insects in this group of plants. I have not repotted most of these since long before the disease started. They are now way over due but I have no urge to repot plants that are being killed by a disease anyway. If I find that there is a cure, I will repot them all.
Remember that 5 plants started symptoms the same week and within several weeks, most of the plants were showing the symptoms. It's not a virus, I'm sure.

Bacteria?
Bacteria is involved, at least sometimes. I doubt that it is the cause of the initial pits. Once the leaves get pitted, some of them them get some black areas that may be a bacteria invading.

Fungus?
Probably. I'm running short of other ideas. I'm still not sure how it migrated to every Phal spread over an area about 5 feet wide. These plants are watered by hand with very little splashing on the leaves, yet the disease spreads to every Phal in the area.
When I  showed this page the first time, a few different people came up with the name microfungus. People found reported cures for this disease. I did NOT manage to try every fungicide that was mentioned. I had Physan on hand and tried some sprays of that first. I also had Phyton 27 and I tried that next. Two or three sprayings. My best hope was triforine (a systemic fungicide often sold as Funginex). Before winter set in, I got in 4 or 5 sprayings of this. I wanted to wait and see if this worked before I tried anything else. It's quite obvious now that the disease continues in all plants that survive.


Now that I have had additional months to watch the plants, I realize that the pitting is not usually the first symptom. My observation that the problem almost always starts on the 2nd newest leaf still holds, but the first symptom is a change in the internal color of the leaf. On yellow or white Phals, the change is from green to yellow as seen in this first picture. The surfaces are still perfect and clear at this point. The 2 spots seen may be the first pits starting but I have the feeling they may be from something else.




This next picture is a pink flowered Phal. Phals with colors like this get purple discolored areas within the leaf. This leaf has been affected just long enough for the first pitting to start. Right now the pitting is barely noticeable but will soon get much worse. This was a mature flowering plant. The roots look bad in this picture but the disease never starts with root problems.



Here is a leaf a little farther along. The pits are pretty obvious now.





The pits usually progress to this. Larger dead and dying areas.
Leaves with this many pits usually turn yellow and fall of in about 2 weeks.






This one, I happened to repot before I thought the new disease was going to kill everything.
In this picture, all the leaves were killed except part of the leaf to the left. It has managed to produce two new, small leaves. Of those 2 new leaves, the mature one has developed the internal discoloration and is well along with the pitting stage. As soon as the youngest leaf stops growing and matures, it will start showing symptoms too.



After several months, all the original leaves are killed. At this point, most of the root system is still alive and side buds sprout into new plants.




Another plant that survives only as a side sprout.  The older leaf is fully involved now.




One more plant that has lost all the original leaves and survives only as side sprouts. (There is a 2nd one on the right, low, coming from between the roots.) The oldest of the leaves (far left) is showing the purple discoloration in the leaf.




This one is different. No pits. The leaf later yellowed and fell off. This may be the same disease or maybe not.





A view of the under side of a leaf. It turned yellow and fell off within 2 weeks.



A plant that held onto a couple of flowers as the disease hit. The inflorescence was eventually diseased too. The black area doesn't  occur, ever, on most plants and is probably a secondary infection.


Thanks for looking.
I would love to have a name for this disease.
A cure would be even better.