Round fungus spots attacking my Paphs. If some of you have insights on a durable solution.

[richgarrison]

Banrot is my goto.... includes both thiomyl and etridiazole... drench and spray...

 

[Ray]

I have used two - Inocucor Garden Solution, now sold as Synergro, I think, and Quantum-Total - but with good results and no negatives, other than the smell.

 

[Cach26]

I wonder if some preventive probiotic treatments (Bacillus or Trichoderma) would be a solution here.

Most likely not, not because they are not useful, simply because the problem is very serious.

And the plant is already infected, these treatments are preventive

 

[Cach26]

The pathogen is in the immediate environment ...., but if you periodically disinfect the shade house structure, benches and floor, and kill it in/on your plants, splashing rain drops will have less of a chance of spreading it back to the plants.

Last week I was visiting a collector of semi-terrestrial species. He is an elderly man, very friendly. Sadly over the years his greenhouse has deteriorated.

It is located at 1500 masl, with a daily humidity of 100%, and a cold-temperate climate.

The polycarbonate roof has fallen down, and has left the Phrags and Paphs exposed to the open air, lately he only has a shade net over them to avoid direct rain on the plants.

And just there, I remembered your thread, as his plants have exactly the same symptoms and brown wounds as yours, mostly the Paphs.

As Mr Ray said, it may be the environment that is so deteriorated and damp. Maybe some of the iron is dripping rust onto the leaves, or the water is too much soaking into the leaves.

As you can see in the photos there are also a lot of dead plants, and although it is a large space there is very little air movement.

 

[Cach26]

Maybe just putting a roof on will make a difference

 

[Ray]

Most likely not, not because they are not useful, simply because the problem is very serious.

And the plant is already infected, these treatments are preventive

Probiotic treatments can be curative. The trick is finding the microbe that attacks the pathogen at issue, which is why complex consortia are preferred. Sort of the "shotgun" approach versus "the rifle" of a single species that may-, or may not be properly aimed.

 

[Cach26]

Thank you Mr. Ray, for the correction .

I was talking to an agronomist who also grows and hybridizes Catleyas, about this issue, he mentions that although they are very profitable, they must be applied weekly in the irrigation, due to the airy and loose substrate of the plants.

 

[Ray]

I was talking to an agronomist who also grows and hybridizes Catleyas, about this issue, he mentions that although they are very profitable, they must be applied weekly in the irrigation, due to the airy and loose substrate of the plants.

I am currently using Quantum-Total. I apply it at about a 1.5-2% dilution every 3 or 4 weeks.

The microbes populate both the media and the plants, so the idea is to maintain a strong population by periodically dose them for reinforcement. Letting the potting media dry definitely reduces the viability of the microbes, but I don’t allow that to happen.

 

[Ozpaph]

I use copper based spray for anthracnose

 

[Russ1992]

Make sure you are providing enough airflow to prevent the leaves from staying wet for too long. That can help prevent future issues.

For what it's worth the plants might also be stressed as your media looks pretty small and dense which can lead the plant to be too wet for too long.

 

[treefrog]

So, I made some more observations. These round spots are most likely due to fungus and each years appears at the start of the rainy season when the climate switch very quickly (in a matter of a few days) from very dry to extremely humid and rainy. While I have not been able to prevent these spots from appearing, an early treatment with copper seems to stop the spreading. Unfortunately, this year, the rain started while I was travelling, and in a matter of about 4 days quite a lot of damage appeared. Sprayed with copper, and everything has been stable for more than a month now. Here are some of this year damage:



The majority of my seedlings are from Sam Tsui (Orchid Inn) and from Xavier (Select Orchids) and for some reasons I cannot explained, it is nearly exclusively plants and seedlings from Sam that are affected (not a single one from Xavier, even though I must have nearly 200 from him). Go figure.
The damage can look quite disfiguring, but I have the luck that the seedlings grow so quickly that in only a few months it wont be noticeable.

 

[CharlesD]

Thanks for the update. Hope everything survives! Does seem like sometimes only experience can bring the solution with problems like these. I would imagine that Xavier's plants were better off from a micronutrient perspective but which micronutrient could the one helping to prevent this is hard to know. That may not be the case either.