My Phal has Pimples
 

Just discovered black pimples on the underside of one of my Phals leaves. What is it?...disease? What should I do with it?... Isolate it from the others, remove the leaf, throw it out?

Do not remove leaves. Do not throw out. It is not necessary to isolate.

Whatever it is, it isn't a problem that will continue to spread.

Grow it the way a Phal should be grown.

Some of my Phals wound up with similar spots due to a stray leaf hopper feeding on them. Some sap feeding insect may have snuck in at some point and sampled yours too.

One of my phals gets spots like this often but I'm never seen any bugs and it seems to grow okay. I wouldn't worry too much

Often these spots are oedema, which is a physiological condition where a plant takes up water faster than it uses or transpires it. (e.g. well watered plant in cool humid air, which can often happen in the winter). Water pressure builds up in cells and they end up bursting, causing little lumps.

I immediately thought of edema too. Different spelling here I think, but I agree.

After nearly 20 years outside the US, my spelling has been affected. Too much influence of UK English (oedema) and latin language spellings (oedème in French) of words!

Thanks to everyone that replied to my post. The edema seems like a logical answer. I have a tendency to let the orchids get quite dry and then soak them thoroughly for about 5 minutes. The pots are well vented and allowed to drain thoroughly, but maybe I should back off the soak time a bit. Otherwise the Phals are all in bloom now and look great otherwise.

Soaking isn't the problem, and 5 minutes really isn't long.

The exact combination of circumstances needed to cause it are more likely to happen in winter- for instance the plants are watered late in the day and then the growing area is cool and humid overnight. I've never seen it on my orchids, but get it every year on my tomato seedlings since I keep those pretty wet. (and potting soil remains saturated a long time, unlike a good quality bark mix)

Edema (probably pronounced oedema) is ussally caused by the plants uptake of water faster than it can than it can transpire it though it’s leaves. Causing small blisters/hematomas where the cells swelled past capacity. Several factors come into play to cause this, and most of the time this is a rare event. Don’t worry much about this, thinking that you, in someway caused this or can stop this from happening. It is good thing, in that, your plant has very happy, strong roots that are working optimally, usually we have the opposite happening. Sometimes they will break open but sometimes they will just stay little blisters. Good luck with your plant.