what is this disease on my phaleonopsis

[lotusbird]

I am so upset, 7 of my beautiful phals are afflicted by this! It seemed to happen in a matter of days, and it spread like wildfire.Very strangely, only the full sized phals and not the minis are affected. None of the other species I have either. So far I have isolated the 7, cut off all the diseased leaves, and doused with cinamon where cut, and was going to repot but I figured I should spray the roots with SOMETHING, but I don't know what this is! Some kind of rot I guess? This is my first experience with disease, I'm totally at a loss here...

Barbara

[Ray]

Looks like sunburn to me.

Phalaenopsis should never see direct sun.

[BellaOrquidea]

Will it be possible for you to post a picture of the whole plant? Physan will be my preferred method to combat fungus, some virus and general desinfectante. But it’s had to advice you w/o seeing the whole plant.

[camille1585]

First thing that came to my mind was sunburn, it looks quite typical of that. If the plants get no direct sun, my second guess would be a bacterial pathogen like Erwinia, which spreads rapidly.

[lotusbird]

I am about 99% sure this is not sunburn. My phals get no direct sun, and 1 time years ago I DID have sunburn on 1, it was nothing like this. The leaf turned yellow and then black and shriveled and fell off. This time they were mostly black and mushy. Many of the roots are yellow. I read an article that phals subjected to prolonged high heat and humidity are subject to rot. We just got over a 2 week period of this. I have cut the leaves of the affected plants, all but 1 plant that I will take a picture of later, and the roots also. The others, I haven't repotted yet, I want to spray the roots, I have no Physan yet, all I have on hand is Sevin and insectcidal soap. I have used Sevin before with good luck, but I don't know if it's appropriate in this instance. Will the phals be ok for a day or so in no medium if I spray the roots daily? I'm thinking they will, as I have 1 in no medium in a basket thats doing great (it's actually blooming, and wasn't affected by whatever this is. I'm sick over this


Barbara

[Gil]

Looks like a rot IMO, but I am no expert. I do let my phals dry out between waterings and they are one orchid I have never had a bit of problem with. The only plant that survived my kill off 11 years ago was my only phal at the time. Have about 10 now.
I probably would heave a phal as fast as I could if the leaves got looking like those but that's just my opinion.
Good luck with it and sorry you have that problem.

P.S. All my phals get tree leaf filtered sunlight through SE facing tinted windows in the summer and just through the tinted windows in the winter. This all occurs to about 11 AM with shade the rest of the day. Never had sunburn.

[camille1585]

So not sunburn.... But I have seen sunburn that looks like that, some exactly like your first photo. In the first days after burning the burnt area is mushy and white-ish with spots, and after that the lesion dries out to the typical dried brown tissue we associate with sunburn.

Why do you want to spray the roots? The problem seems to be with the leaves as you describe it. I would not be worried about the yellow roots, that's normal. The only roots that will be green are the ones that get light. So many of the roots towards the inside of the pot are not going to be green and are often yellow, cream, whitish or brownish. Color doesn't matter, a healthy root is always firm.

As to temperature and humidity I'm not sure that that alone is the problem. Phals are tropical plants, and they thrive in warm humid conditions. Where you might run into problems is warm and humid but with no air circulation. That's the trifecta for disease development, as pathogens love those conditions. As long as the air is moving a bit the Phals should be fine.

As to treatment, for fast spreading rot usually the best course of action is to cut off all affected tissue, taking a 1-2cm margin of healthy tissue, and sterilizing the blade after each cut. Being in Europe, I can't advise you on chemical treatment since I don't know what's available to you.

[lotusbird]

Exactly right, Camille. Hot, humid and little to no air circulation. And I KNEW this was an invitation for disease, I just wasn't thinking, stupid,stupid stupid! To top it off the phals in my plant room with the fans running were not affected, the affected ones were in the living room with leaded glass windows that don't open, think I could make a connection there?
Anyway, I already cut away the damaged tissue with sterilized shears, and dusted the cuts with cinnamon, I managed to get my hands on some Physan, I was going to soak each Phal in it for 10 minutes at 2 teaspoons per gallon but after reading your post perhaps I should wait and see if anything reappears? What do you think?

Barbara

[camille1585]

I don't know Physan since we don't have it here, so hopefully others will chime in. I intentionally did not comment on how/what to treat with as I've been lucky to have had rot like that once, many years ago. I caught it early and removing the affected leaf was enough to stop it.

[Roberta]

I would not soak the roots in Physan - it's a surface-acting fungicide, not a systemic. And as has been pointed out, the roots don't show signs of rot. You also don't want to potentially kill beneficial organisms that may be in the roots.