hello. i just got a job as indoor plant maintenance technician and all of our plants are in containers with no drainage holes. recently, i discovered that a specific ponytail plant which had been okay in the previous week has its leaves turned partially yellowish; brown spots/patches surrounded by yellow discoloration. further observation showed that the leaves wilted/rot from the point of attachment to the stem and easily pull out of the stem. i suspect crown rot but I'm not sure because its pretty dry and sunny around here. and indeed if it's crown rot, what can i do?. any non-toxic chemical suggestion will be appreciated. please note that the plants are indoors always in an office environment. any help will be appreciated. thanks. pics are attached for clarification
If none of the pots have drainage holes you must be very careful with the watering. The plants need to only be watered when they are dry all the way to within an inch or 2 of the bottom of the pot. To determine this you can cut bamboo skewers or dowel rods about 1 inch longer than the depth of the soil in the pot. Then insert the skewers in the soil and leave them there. When you go to tend the plants you can pull the skewers out and if more than the bottom 1 or 2 inches of the skewer is wet do not water it. Overwatering kills more plants than underwatering.
As for the ponytail palm if all the leaves will pull off I am sure it has been severely overwatered for some time. If you can pull all the leaves off then trim the plant down to an inch or 2 of the stalk and drain as much water as possible off by laying the pot on it's side in a sink to dry it out. Then set it in a bright corner and let it get totally dry. It may sprout a new plant from the roots if there are any roots left. I suspect the plant is totally dead and at this point it is your predesessors fault, not yours. Just be very careful from now on not to overwater the plants or convince the owners that they need to be repotted into pots with drainage holes. It is extremely difficult to keep plants alive in pots that do not have drainage holes. Good luck!!