Not sure what this is...

[Pilot]

...so maybe someone on here can help. I have an sh pot full of Onc twinkles and one species Onc that is used in the twinkle lines.


But what is going on with the leaves? I have it in sh, the affected leaves are both old and new, though more of the old ones are affected than the new ones, and I have it on a heating mat. Roots and bulbs actively growing and I water weakly weekly with a 20, 10, 20 grow more urea free fertilizer, with Epsom salt added, just a pinch to a gallon bucket, and they're grown under lights, at least until it's warm enough to move them outside.

Any ideas?

[Kostas]

Seems like Pythium to me. Definitely check the roots!!!
If its an important plant,let it soak in fungicide as it is,let it drain an hour latter and let it dry out. Once dry after a few days,repot in something much more airy and that dries out faster. If you wish to keep it sh again,use a bigger size sh and keep less water at the bottom. Oncidium seem to require very good air circulation at their roots and easily get fungus damaged roots when they dont get enough. They also seem to like to dry out completely.

[BruceP]

Likely fungal (anthracnose). Cut off affected parts of leaves and treat the plant with a systemic fungicide like Thiomyl. Also, keep cooler and drier.

[Leafmite]

I have to agree. If it was a humidity problem or fertilizer burn, it is usually just the tips.

[Pilot]

Hmm ok... I'll treat it then. I have a fungicide. The affected areas seem to most affect just the tips.

I have several other larger Oncs and they love sh, so why not these guys?

[Kostas]

Young plants are more susceptible than adults and probably use less water than the adult Oncidium you grow. As a result,the mature Oncidium probably dry out faster and thus are growing in better conditions than these young plants.
Even if you do cure them will fungicide,which i am sure you will,they will get it again a few months later,when the fungicide action wears off, unless you change their culture somewhat. For a start,if you dont want to move them to bigger size sh,you can make a hole lower down so that the container has a smaller reservoir and thus it allows them to be drier and dry out faster.

[Pilot]

The container they're in is 2 gallons. Does it really need to be larger? I'll get a photo to show you the full set up.

[Pilot]

Here's a pic of the whole container. Yes it is glass and yes it has a hole (yeah for diamond bits!). The water line is just below half way point between the bottom of the yellow tag and the bottom of the pot. Hopefully you can see it!

[Kostas]

The setup doesnt seem bad but they do seem a little deeply buried. I would remove all material to where the roots emerge or pull them up to that point if they can be pulled without damage. A bigger diameter material would be better for them as Oncidium can grow well with little water and more aeration.

[Pilot]

Great thank you for the info!