6 Ft Tall Pencil Plant Has A Wide Diameter Center Trunk, Now Has Black Plaque-like Areas On The Trunk???

Question

The plant is about six years old and at one time was over ten feet. I cut it back to about four feet several years ago. It now has a younger middle trunk growing about the original one. I haven’t looked closely at the plant for at least a month. The black plaque- like patches are on the original trunk, heavier towards the bottom. It appears that are moving upwards. The upper plaques are smaller in size.

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Answer 1

It may be stem rot. This article describes the problem and how to correct it. I also would take some cuttings off the top of healthy tissue just in case you lose it.

https://www.gardeningknowhow.com/ornamental/cacti-succulents/scgen/stem-rot-of-cactus.htm