Problem with leaves...help..!

[biothanasis]

Hi all,

Does anyone have an idea why would leaves from vandaceous (and pleurothallidinae) plants fall off without any sign of decay??? Roots are fine and there is no evidence of bacterial rot, yellowing (sometimes there is though...) etc.

Could high temprature cause something like this? Should I start providing epsom salts, to help plants recover or something? What is the dosage in a litre of water? Anything else?? (cooling would be very difficult this period...)

Any help would be appreciated. TYIA

 

[paphioboy]

Pics (of whole plant and fallen leaves)..? I have had problems with vandas, only when the root system is unhappy. They may shed up to several basal leaves and you just have to wait for the roots to recover before they regrow new leaves.

 

[biothanasis]

Thank you for the reply! I have tossed the fallen leaves...

I cannot provide photos at the moment as my camera's memory card is broken... Ah.... What did you do until they grew new roots?? What if all leaves fell? Was there any opportunity to put new growth or grow roots? TYIA

 

[SlipperFan]

How are the roots on your plant?

 

[Rick]

Vandaceous covers lots of ground for light and temperature tolerance. Low light Phalaenopsis or high light Vandas? Vanda tricolor likes warm temps, but Vanda roebelingii likes cooler temps.

Heat could be an issue for lots of Pleurothallids though.

Heat and low humidity together is even worse. What is the RH?

Yellowing and dropping older leaves in large amounts sounds like the plant may be trying to grow, and reabsorbing nutrients in the old leaves. Epsom salts would probably help, and certainly not hurt.

What is the hardness of your irrigation water?

 

[SelectOrchids]

In my experience you can get this from poor root system and heat at the same time, combined with pythium. If the roots are actively growing and the plant is not infected all is fine. Otherwise, when the plant is stressed (poor roots) or when the heat comes, pythium resumes and kills the plant. Pythium usually stays dormant during the cooler months, which does not mean that the plant is not infected. That's why many people see 'bacterial rot' during summer time. It is not bacterial first, and second, the plants most of the time were long time infected by pythium. Leaves of phals, vandaceous, and masdevallias just drop immediately without any warning. For paphs, it makes watery areas and brownish colors. It is the same disease on different plants (paphs do not drop their leaves so the symptoms are different)

 

[paphioboy]

For paphs, it makes watery areas and brownish colors. It is the same disease on different plants (paphs do not drop their leaves so the symptoms are different)

Interesting you should say that. I thought the common 'soft rot' on paphs was caused by the bacterium Erwinia cypripedii... Pythium infection is obvious on roots (brown and mushy, basically damped off and mostly affects seedlings). If it is Pythium, you will see fine greyish fungal hyphae growing on the base of the bulb, near the rhizome... From my experience, anyway..

 

[SelectOrchids]

Interesting you should say that. I thought the common 'soft rot' on paphs was caused by the bacterium Erwinia cypripedii... Pythium infection is obvious on roots (brown and mushy, basically damped off and mostly affects seedlings). If it is Pythium, you will see fine greyish fungal hyphae growing on the base of the bulb, near the rhizome... From my experience, anyway..

No, the soft rot is caused by pythium and sometimes a strain of phytophthora. I made PCR analysis and that was clear.

You have good photos of pythium here:
http://www.hark-orchideen.de/Pflanzenschutz/Phythium/bilder.php?lang=en&navID=99

The tissues are very watery, disease can progress overnight.

The soft rot with mycelium is either rhizoctonia or fusarium.

Got a photo of one of those soft fungal rots here:
http://www.hark-orchideen.de/Pflanzenschutz/Sclerotium/bilder.php?lang=en&navID=99


Real erwinia cypripedii, PCR or microscope confirmed, is what makes a dry brownish color and yellow leaves, but it is never ever 'wet'. There is a picture here:

That looks exactly like that. It is never 'wet'.

 

[Bjorn]

So, how to avoid it? Any cultural practises that would help?

 

[paphioboy]

Thanks for the clarification, roth. This is interesting (I am interested in plant diseases ). Does that mean the common soft rot on Phalaenopsis leaves is also caused by Pythium instead of Erwinia, as stated in several books I have read? I know Pythium sp. grow very fast in vitro (fills a petri dish in 1-2 days) and also in soil, which may explain the overnight progress of disease observed... I just didn't think it would grow on 'dry' surfaces like leaf tissue, unless damage has occurred or water has pooled at the axils.

 

[biothanasis]

Hi all,

Thank you for the nice answers... From what Roth says it must be pythium.... But how do we treat plants with it??

Also Rick has a point there... But unfortunatelly I have no idea what TDS my water has. I use tap water, which has at least stayed overnight to let the chlorine evaporate.

The problem has occured on a phal, a stereochilus (recently arrived) and all the pleurothallis I had (in the pleurothallis the symptoms are the same as described by Roth). [Let's say the pleurothallidinae are more succeptible to stress...]. The phal has silvery-white roots and almost the same are the roots of one remaining pleurothallis. The stereochilus has a couple of roots that are hiden in a thin layer of sphagnum moss, which I mounted on a piece of cork. The stereochilus lost most of its leaves in 2-3days. There is only one left on the top...What could I do to save it???

Roth, I have also lost some paphs from the same disease seen on the photos you provided. Thank you! If you know any easy to apply treatment, please let me know! TYVMIA.

 

[NYEric]

Treat them, cool them down, and improve air flow.

 

[biothanasis]

Unfortunatelly I do not have a way to cool them down... So I think I will loose them and then buy others... LOL

 

[Paphman910]

You think it is bad to get diease on your plants. In Canada, the government have banned all systemic pesticide and fungicide for non-commercial use! It really sucks if your prized collection gets infected by rust!

Paphman910

 

[biothanasis]

Eeemmm.... I do not think it is bad... it is the way it is... but if I can save a plant with a homemade treatment of jst improve the conditions I could offer to the plant then I think it would be nice both for me and the plant ...

Do you happen to have any problem at present with your plants?

 

[Paphman910]

Eeemmm.... I do not think it is bad... it is the way it is... but if I can save a plant with a homemade treatment of jst improve the conditions I could offer to the plant then I think it would be nice both for me and the plant ...

Do you happen to have any problem at present with your plants?

Last year I had problems with losing lower leaves to rot and the rot smelled nasty. It seems to occur when the temperature got over 90 F and humidity of 95% plus just watered the plants the day before. I think lack of air flow and light caused it.

This year I don't have problem as I added a fan to circulate the air but the plants need to be watered every two days!

I think the fungi and bacterial occurs naturally in the air and around us and when the conditions are right they will thrive and destroy your orchids.

My plants seems to be getting alot of algae growth in the last two years and the weather has been strange.

Paphman910

 

[paphioboy]

You think it is bad to get diease on your plants. In Canada, the government have banned all systemic pesticide and fungicide for non-commercial use! It really sucks if your prized collection gets infected by rust!

Paphman910

Interesting. So what do you use for treating plants? Any of the organic mixtures? Neem oil? I agree with you that airflow is very important in preventing rots and other nasty things, especially in a humid climate where I live...

 

[Marc]

Interesting. So what do you use for treating plants? Any of the organic mixtures? Neem oil? I agree with you that airflow is very important in preventing rots and other nasty things, especially in a humid climate where I live...

Politics making the world a better place again, sigh................ :S

 

[Rick]

Hi all,

Also Rick has a point there... But unfortunatelly I have no idea what TDS my water has. I use tap water, which has at least stayed overnight to let the chlorine evaporate.

In the US you could go to your local health department or municipal water regulator and ask for a report. I couldn't tell you about getting reports in Greece would be like (or if you are on a well, then you would be on your own anyway).

Conductivity (TDS) meters are pretty cheap from garden centers too.

I have a pretty good paper that for agricultural plants demonstrating that disease agents are often the result of poor or imbalance nutrition (generally the ratio of K, Ca, and Mg. You could probably find a bacteria or fungus if you look for it, and might even get some positive effects with a treatment for such disease agents. But without providing the plants with the proper nutrition, you would only be providing a short term, topical, aid without fixing the underlying problem. Ultimately it would happen again farther down the line.

Check through this thread too.
http://www.slippertalk.com/forum/showthread.php?t=21871

 

[biothanasis]

Thank you Rick!!!