Black, wet spots on Phal leaves after re-potting - Help!
 

Dear all,

Signed up to the forum to ask this specific question as after trawling the internet I'm still uncertain as to what I'm dealing with...

I re-potted my old Phal about two weeks ago. Over the following week I've noticed multiple black, well circumscribed lesions appearing over most of the leaves. They are mushy, but don't leak when pressed. One of the leaves seemed to have it particularly bad at the base; it turned yellow and I removed it. Another leaf seems to be going the same way. The lesions don't appear to be expanding in size and have remained static over the last week.

I've searched the internet and the nearest similar problem I can find is a bacterial infection like black rot, although I seem to be dealing with very discrete lesions, quite different to a large confluent lesion you get in black rot.

I've kept it separate from my other orchids and have treated with an all purpose fungicide containing tebuconazole which I'm not convinced is making any difference.

Does anyone know what I'm dealing with here? What's the best course of action?? I'd rather not just bin it as it was by far my healthiest orchid pre re-potting. I've read about cutting all the affected leaves off but that would leave only two which I'm fairly sure would kill it anyway? Any recommendations on brands of bactericides I could try (bearing in mind I live in the UK where Physan is banned)? Would trying hydrogen peroxide be worthwhile?

Any help greatly appreciated!

It almost looks like the spots started as edema spots from too much water the plant took in. Now it is turning into infection at the spots. I would put a dab of cinnamon powder on any spot that is moist. Also if it is at the base put cinnamon there to keep it from spreading or the crown may rot. (don't put on roots)

That is so unusual and circuscribed. If you have a university near you with an agronomy or biology department, somebody there will probably be able to look at it under a microscope and find out what it is.

That is Acidovorax. You can find out more about it at Orchid Pests, Orchid Diseases

To save your plant you need to disfigure it a bit. First, use a very sharp blade (flame sterilized and cooled X-acto knife is perfect). Cut through healthy tissue between the spots and the crown/stem of the plant. If the spot is small, you may be able to cut a hole around the spot. Do this with every spot. Allow the cuts to dry for a few hours. Then, use a paper towel or cotton swab and hydrogen peroxide, wipe all leaf surfaces top and bottom (don't drench, especially roots).

Set the plant aside separate from your others. Don't water and keep watch on it daily for new spots. Repeat the cut/peroxide procedure if new spots appear. If there are no new spots after a week, carefully resume watering just the roots but keep isolated and keep watching it. When you are certain there are no more new spots, I would consider repotting (the bacteria may be in the old medium).


Added later: you should consider adding calcium into your nutrition regimen if you are not doing this already. Calcium helps with disease prevention.

I agree with whisper....such a shame! but, I also noticed on your first pic, you have a nice spike coming! its so sad your plant will look like a rabbit got a hold of it!