My night-blooming cactus has been developing thick brown scab-like growths on new leaves for about a year. Once they appear, they tend to spread quickly and look like they kill the leaves. I repotted a few months ago and the new growth looking great! No signs of black growth, however now it seems to be returning. I was spraying with Neem oil weekly and not noticing effect. Any advice would be so helpful!
This is bacterial. Make sure that this is planted in a cactus mix, and neglected, as far as watering goes. They do not do well in moist soils.
From here, you will need a strong fungicide. I would contact your local agricultural extension service to make sure of which one's are OK to use in your area. Wettable sulfur is a good one for general use, and is usually safe for any people around. It makes for a decent bactericide. sulfur is, generally, lacking from the soil anyway.
https://www.gardeningknowhow.com/garden-how-to/info/using-fungicides-in-garden.htm
https://www.gardeningknowhow.com/garden-how-to/info/what-is-copper-fungicide.htm
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/side-dressing-with-sulfur.htm
https://www.gardeningknowhow.com/ornamental/cacti-succulents/night-blooming-cereus
I don't know very well how to keep the queen of the night flowers. happy if you can provide me tips to keep the queen of the night flowers.
thru early fall. It seems to love the Oklahoma summer heat and humidity. Something eats on the leaves when it is outside. I'm assuming it's some sort of insect. What do you recommend to treat the plant with? Also, what are the tall spikes in the picture?
The long stems are tendrils reaching for more light and is normal. Try to identify the insects or caterpillars that are eating the plant leaves before treating it. These articles should help.
https://www.gardeningknowhow.com/ornamental/cacti-succulents/scgen/how-to-deal-with-succulent-pests.htm
https://www.gardeningknowhow.com/plant-problems/pests/animals/nocturnal-pests.htm