Night Blooming Cereus

Question: Thank you for answering my question about this plant. What is causing it to blacken and dessicate and what should I do?

Plant: Large indoor Night blooming cereusHad it 30 years
Leaves and stems and buds affected
Margins of leaves browning and dessicated
Stems blackened and black scabby spots but no obvious “removable “scale”, buds blacken too
Throughout plant
Noticed for the past year, transplanted to epoma organic succulent mix/ desert plant mix and it worsened
I allow plant to dry out, big pot, usually water it fast with quarts of water
Gets direct sun only in afternoon, west facing window, white waffle blinds pulled 1/2 way down
Current management: Sprayed once with bonuses insecticidal soap at least once with dish soap mix, also safer house plant sticky stakes.
No fertilizer (new potting soil)Insects: gnats but with some webs all winter, so used dish soap spray, tried rubbing alcohol once, etc.
Don’t see gnats now.
Desiccation for at least the past year maybe two (at one point 2018 plant also got sunburn outside) but gnats for 2-4 years on and off
Plant is in dining room. Gnats have been in other plants too. But no big problems. 
Have taken cuttings of least affected parts and put in water hoping to save the plant.

responder: UVM Extension Master Gardener Program Volunteer  Replied August 23, 2024, 11:02 AM EDT
response: Thanks VERY much, Judy. Have a wonderful weekend.PatOn Aug 23, 2024, at 10:02 AM, Ask Extension wrote:﻿

responder: UVM Extension Master Gardener Program Volunteer  Replied August 23, 2024, 11:34 AM EDT
response: Dear Lise: Thanks for contacting the UVM Extension Master Gardener Helpline with your question about a 30 year old Epiphyllum that has browning leaves and dessicated, blackened stems. To answer your question, we consulted with Judy, our resident expert on house plants. Here is her response:  Epiphyllum oxypetalum (Epi’s) (the Queen of the Night) enjoys medium light indoors and a shady spot outdoors during the warm weather season, never full sun. This plant likes it warm with high humidity. So it's best to run a humidifier when the humidity is low. Never let the soil stay wet or you will invite soil gnats. Let the soil dry between waterings. This is a plant native to tropical Central America and Southern Mexico. In its native habitat, the flowers are pollinated by bats and its fruits are edible. Overwatering and underwatering are the usual suspects when it comes to brown spots. Too much water leads to root rot, while too little water dries the plants out. Both extremes stress your Epi, manifesting itself in dreaded brown marks. Brown spots can also be a sign of fungal disease. It's best to prune out the affected areas and adjust plant care to prevent spread of the disease. Try to balance light and moisture.  Epi’s thrive on stability. Environmental stressors trigger problems. Sudden fluctuations in temperatures will shock the plant. Drafts or changes in location will also cause problems. Judy recommends investing in a $10 water meter to be sure that the top few inches of soil are dry before watering again. Alternatively, you could use a wooden dowl to test soil moisture. Use a well-draining succulent/cactus soil mix. Add some perlite if the soil mix is a bit heavy. Remember to keep the plant in part-shade or bright indirect light.  For additional information see the following resource:  Epiphyllum oxypetalum (Dutchman's Pipe Cactus, Jungle Cactus, Lady of the Night, Night-blooming Cactus, Night-blooming Caereus, Orchid Cactus, Queen of the Night) | North Carolina Extension Gardener Plant Toolbox (ncsu.edu) We hope that this information is helpful. If you have additional questions, please let us know. Good luck. Pat

responder: The Question Asker Replied August 25, 2024, 12:05 PM EDT
response: Thank you very much. I am going to try several approaches. Hoping it is not a mold.Thanks for being there!LiseCornwall, VTOn Fri, Aug 23, 2024 at 11:02 AM Ask Extension <<personal data hidden>> wrote: