Mass Phalaenopsis Root Rot Situation?

[jje10001]

Hi all,

Just an emergency- this week some mysterious root rot infection has spread really quickly among a section of my phalaenopsis collection.

The last week these phals were still healthy and growing roots, but over the course of a week, many roots started darkening and getting mushy all at once, accompanied by the appearance of fungal filaments. Some of the sphagnum at the top of the pot also started getting moldy, for some reason (never happened before this).

The rest of the plant seems unaffected, and phals that were grown drier, or located away from this particular collection also seem unaffected.

These phals were all potted in orchiata mixed with leca, with a bit of moss at the top, and there was a fan running in the room during the day.

Any ideas as to the cause? Not sure if it's fungal or bacterial, nor of the ways to treat this (I don't have access to systematics where I am).