Night blooming Cereus has parts of leaf that are dark brown & dry on one leaf at the top end of the plant. What could cause this?

Question

This is an old plant. Thinking it might need new soil.

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Answer 1

This appears to be a fungal infection. It can happen from the soil remaining wet for too long, without a dryout between.

This can be treated with a fungicide. This article will help: https://www.gardeningknowhow.com/garden-how-to/info/using-fungicides-in-garden.htm

This article will help you with the care of the plant: https://www.gardeningknowhow.com/ornamental/cacti-succulents/night-blooming-cereus/night-blooming-cereus.htm