Brand new Oncidium dying...blackish brown spots on leaves

[mtnfir]

Hey all,
I am brand new to this board and pretty new to orchids. About two weeks ago I purchased a lovely oncidium Wildcat # 13. It has an enormous spike full of lovely flowers. It is planted in a coconut bark medium and I have not yet watered it as it still feels moist. The psuedobulbs are all shriveled up and the were when I bought it. I assumed that this was typical of this particular variety. Over the past few days I have noticed a greying/browing of two leaves that is spreading pretty fast. It is under a south facing skylight, but never gets direct sun. I took it out of the pot yesterday and mushed one of the coconut bark chunks and water came out.
Help ...what is going on?
Thanks in advance.
Carl

[silken]

welcome to Orchid Board!

Your pictures indicate that the pseudobulbs were partly buried which shouldn't happen. This could cause rotting of them and then the leaves would die off. I also see a lot of fine coconut fiber or something on top which could prevent good air flow to the roots which they need.

How were the roots when you un-potted it?

After cutting off any dead mushy roots, I would treat the plant with something like Physan (fungicide/bactericide) and pot it into a small pot that is not much larger than the root base. Make sure it has lots of holes for aeration and good drainage. I would use a medium to fine bark that has been soaked well. Oncidiums usually don't like to dry out completely but close to it before watering again. If it is lacking roots, I would suggest finding some kelp (seaweed) to add to the water when it is watered. I even soak roots in it before re-potting. It seems to stimulate root growth well. It can be found at many hydroponics stores.

[mtnfir]

I repotted the orchid in a medium bark mixture that was soaked in a weak water/seaweed solution as you suggested. The roots were all bound up so I untangled them a bit. Much smaller pot now too that has holes. I also cut off the problematic leaves. I found a good orchid disease resource complete with photos. I am wondering if it might be anthracnose. What are your thoughts on that.
Thanks
Carl

[ALToronto]

If you potted it in bark, why is there so much coconut coir on top? Get rid of it, it's only suffocating the roots. I wouldn't look for rare diseases when the problem is most likely with the culture.

[silken]

Originally Posted by ALToronto

If you potted it in bark, why is there so much coconut coir on top? Get rid of it, it's only suffocating the roots. I wouldn't look for rare diseases when the problem is most likely with the culture.

I think he has re-potted it since in bark and a smaller pot.

---------- Post added at 11:18 AM ---------- Previous post was at 11:12 AM ----------

Originally Posted by mtnfir

I repotted the orchid in a medium bark mixture that was soaked in a weak water/seaweed solution as you suggested. The roots were all bound up so I untangled them a bit. Much smaller pot now too that has holes. I also cut off the problematic leaves. I found a good orchid disease resource complete with photos. I am wondering if it might be anthracnose. What are your thoughts on that.
Thanks
Carl

I don't think I would worry too much about that leaf. Just as well you removed it tho. If you have an anti-fungal such as Physan you could treat it just as a precaution. Don't use more than instructions say on the bottle. I think now it just needs to get ready to develop a new growth which will produce new roots and it should be fine. I would use the seaweed for a few weeks. Then stop for a month and use again. supposedly you don't use it all the time but at intervals. Remember new bark dries out quicker than slightly aged bark. I like to use a bamboo kebab skewer (the little thin ones) placed down into the centre of the pot. I pull it out and see how wet it is before watering. It should only be just barely damp or dry, not wet before you water. Oncids don't like to be dry for long tho. Usually just approaching dryness if that makes sense.

[mtnfir]

Thanks for the help AT and S. The pictures posted are how it came to me. No coconut now, and in a proper orchid pot.
I like the bamboo idea. I guess I just leave it in there and pull out every now and then to assess moisture levels. I'll give that a go.
C

[silken]

Originally Posted by mtnfir

Thanks for the help AT and S. The pictures posted are how it came to me. No coconut now, and in a proper orchid pot.
I like the bamboo idea. I guess I just leave it in there and pull out every now and then to assess moisture levels. I'll give that a go.
C

Good luck with your plant. Yes, I just leave my bamboo skewer in the same place and try and place it back there so you don't stab roots everywhere. Then it is in there like the bark and either dry or varying degrees of wet just like the bark. I use them on most of my orchids.