Help Identifying Pathogen on Phalaenopsis - leaf spots possible crown blackening

[JoieQuinn]

I have had this phalaenopsis for 1.5-2 years, and I have not had problems with it. It has always had some blackening/discoloration compared to my other phalaenopsis, but I thought that was just its coloration.

Recently I got spider mites and treated everything with a soap/alcohol mixture that I found online. The treatment worked well for the mites, but the drenching of the soil killed a lot of my plants, and my orchids seemed unhappy. I repotted them into a volcanic rock medium, which I realized quickly was just too dry for them, so I repotted them again into an orchid medium about 1.5 weeks later (but a lot of damage had been done to the roots - I removed a lot of bad roots on the other orchid (not pictured here), but the orchid in question was actually pretty ok root-wise at that time).

It has been about 3 weeks since repotting, and yesterday -when going to water it - I noticed a pretty badly diseased leaf (pictured). The leaf underneath that one also seems affected, though early stages. The crown also seems to have some blackening (but I am pretty sure this has always been this black/purple discoloration), and I noticed today that the visible root also seems to have some blackening.

I have consulted the St. Augustine link multiple times, and I asked my local extension program, but I have not been able to lock down a solid cause/pathogen that is affecting my orchid. I am hoping someone on here might have some insight for how/if I can save this orchid and what might be affecting it.

I never mist the orchids. I water them once a week. They live in my kitchen, which is not very humid right now.

[estación seca]

Welcome to the Orchid Board.

What are your temperatures day/night? Is it near a cold window?

[JoieQuinn]

Thank you!

The temperature is pretty consistently 70 degrees (F) and the humidity right now is 44%. It is about 2 feet away from a window, but there is a closed blind on the window, and it is not cold in the surrounding area.

[estación seca]

It looks like temperature damage. Any chance it got splashed with cold or warm water?

[JoieQuinn]

It hasn't been splashed with water, but I did soak the inner pot & plant in filtered water last week (for 5 minutes, then I allowed it to drain for 20 minutes before placing it back in the outer pot.
Could the damage be from that?

[Dusty Ol' Man]

Originally Posted by JoieQuinn

It hasn't been splashed with water, but I did soak the inner pot & plant in filtered water last week (for 5 minutes, then I allowed it to drain for 20 minutes before placing it back in the outer pot.
Could the damage be from that?

I wouldn't think so. I'm not much help with this.

[Leafmite]

The crown looks okay to me. The leaves look as though they have some sort of fungus infection or, as someone else mentioned, cold/heat damage (but the latter is unlikely with your temperatures). I am going to guess it is a fungus issue. When an orchid is stressed, their immunity is compromised and they are less likely able to ward off infections. If this is spreading, it might be necessary to use a sharp blade and remove the infected leaves (treating the cuts with alcohol and then cinnamon). If it is not spreading, it is better to let the leaf remain until there are more new leaves.

To prevent the roots from deteriorating after potting an orchid, I always keep the new medium dry for a few days (I use 1/4 inch lava rock). It gives the roots a chance to heal in case I damaged the roots during the potting process. I learned this when I started growing Angraecums and it is a good trick to helping the orchids adjust in a new medium.

[JoieQuinn]

Thank you so much everyone for all the help and advice.

I will monitor it for a couple of days and see if it is spreading. Would treating with an antifungal not be necessary?

Thanks again!

[Dimples]

I’ll toss another variable into the mix, pest treatments shouldn’t kill regular houseplants. If it did, you may have made the solution too strong, left it on too long, or not rinsed well enough. Alcohol on roots is generally a no-no.

How much light are they getting? What direction does the window face? What state are you in?

[JoieQuinn]

It wasn't the actual treatment that killed the others, I don't think. It was the amount of water; I think I waterlogged some of the plants. Just to be clear, the orchids seemed ok with the treatment (I just wanted to be thorough in their history, so everyone had a complete history). Those treatments were about mid-October.

They get indirect light from the shaded window about 2 feet away (east-facing), and they get indirect light from an unshaded window about 5-7 feet away (south-facing). They also get indirect light from some LED grow lights that are on other plants in my kitchen (no direct lights on the orchids though).