Paph leaf problem - Help!
 

I have a young Paph. Prince Edward of York with a 12" leaf span. One of the leaves got a soft black rot on the leaf tip. I used a sterile blade and cut it off below the infected area and dipped the new cut end into a concentrated mixture of a systemic fungicide but now a week later I've noticed the rot is continuing down from the treated cut. If anybody can please help me identity what is going on?

Can you post a picture please?

Are you sure it is fungal infection? Using fungicide for bacterial infection (or vice versa) is not that effective. Also, what systemic fungicide did you use? If you use concentrated/undiluted fungicide, the leaves may be dying from the toxicity. Is this fungicide recommended for regional application? I think most of us use systemics by drenching or spraying the entire plant.

Thank you both for responding. Sorry, I cannot post a picture at this time. The fungicide I used is a liquid systemic fungicide II by fertilome. The active ingredient is Propiconazole. When doing a general preventive spraying in the greenhouse I dilute according to directions but out of desperation I just dipped the fresh cut end of the leaf directly into the container (undiluted) I just read on the label that this fungicide will not cure an existing infection. It is strictly a preventative treatment! So, if the infection is bacterial, what do I get for it? By the way, only 1 leaf is infectgeted so far. Please let me know soon so that I can something this weekend. Thanks!

I guess I'm curious which leaf it is? If you dipped a sick plant into your container of stuff, you will surely want to be careful about cross-contamination.

Without a picture, it's hard to say more. However, I had some soft rot on a St. Swithin once, I cut it, and it kept going - so, I cut it even more, and was sure to use a sterile instrument. I use stainless bonsai shears and get them red hot with a flame and make the cut while it's still hot. This makes a good clean cut and cauterizes at the same time. Sometimes you have to be more drastic because 'whatever' has spread more than it seems. When I did this, the rest of the plant was fine after.

Best to you and your plant!

I did not submerge the whole plant, only the cut end of that one infected leaf. Thank you so much for letting me know that you used a red hot sterile cut and that it stopped you plant's infection. I will do that on mine asap. Thanks again!

I don't know well about the fungicide you used. This might be overgneralization, but bacterial infection seems to progress more rapidly than fungal infection.

I have used Phyton 27 for Pseudomonas-like infection. Probably it may be better to continue mechanical removal like Jermy suggested before going to the systemic stuff. You might want to dissolve a regular 325mg aspirin pill in a gallon of water and folliar spray it, too.

Thank you for your input. Dissolve 1 325 mg aspirin in a gallon? How cool! Is this an inexpensive alternative for a preventive spray for bacterial infections?

I'm not completely convinced that aspirin foliar spray and drenching is effective, and I shouldn't mention something which doesn't have enough scientific evidence. Some one mentioned it in one of the forum, so I looked into it, and started to use it earlier this year (for stressed plants, e.g. after importation or deflasking, or plants with slight sign of some infection). It is difficult to tell the positive effects (from psychological placebo effects), but I can say that it doesn't seem to be harmful at least.

Aspirin is a modified salicylic acid (SA). My knowledge is superficial, but I briefly read a review paper about plant physiology related to SA. SA is involved in many plant physiological processes, and it is also involved in plant defense system. Without getting into details, SA causes the death of infected cells (to minimize the spread of disease), and also it is a key molecule to signal neighboring healthy cells to increase the investment to defense system. So there is a potential to be useful for orchids. Now, things I don't know is whether the modified form of SA (aspirin) has the same functionality as the natural SA, and whether the folliar spray/drenching is an effective method of delivery.

It is not a substitute for fungicide/bactericide, though. It could be similar to "immune" booster.

Thank you! Very interesting!