Is fungus going to kill off my dragonfruit cactus?

[desertcroc]

Hi all,

I live in coastal San Diego and have been growing a dragonfruit cactus for the last year. It started as a 2-foot section, and is now generally flourishing

Full plant

However, I've started finding branches with black spots on them. I googled around, and it sounds like it could be a fungus and the general advice seems that there is no cure. I've hacked off many of the branches with it, just to see if it will help, but any other suggestions or even an identification would be much appreciated!

Affected branches

[Gary350]

I grew some of that cactus for a while when I lived in Phoenix area. I had mine planted in the yard in AZ soil near the house. My cactus had full sun all morning until about 12 noon then the house shaded the cactus the rest of the day. I watered my cactus once a week at first then not much water after that maybe a tiny squirt from a water bottle when I thought about it. Then we had 2 weeks of rain late November the cactus got black spots and died. Some cactus are very sensitive to too much water and some are not. Do Google search see if you can learn where your cactus is originally from and what type weather they have.

I learned that most if the cactus in the Phoenix area are not native to that area. It is hot and dry and cactus native to that area do not like to be over watered and also need very sell drained dry soil. Cactus near Tucson and Flagstaff are high elevation cactus 5000 ft where they have snow and rain cactus native to that area does good with too much water.

Cactus is a crazy plant it can survive extreme weather, extremely bad soil, snow, ice, blistering hot 115 degree sun but if you give cactus better soil, lots of shade with only 2 hours of sun per day, well drained soil, and a tiny bit more water that it usually gets some cactus will grow as fast as grass and weeds.

Soil needs to be so well drained for some cactus when you water the plant in the pot the water needs to run right out the bottom of the pot. Roots are like a dry sponge they soak up water fast. You see the water you just pored into the pot run out the bottom 2 seconds later you think that is not good but it is for some cactus.

Save all those cuttings and plant them. They will grow horizontal, vertical, right side up or upside down. Horizontal will give you 3 to 5 plants growing out of the sides. Experiment to see what you learn. Mix 5% potting soil with 95% child play sand in 1 pot. Then try 10% potting soil in another pot and 20% and 30% in other pots 50%, 75%, 100%, you have enough cutting to experiment with. Put some in a location so they get 2 or 3 hours of morning sun and shade the rest of the day, some in 6 hours of sun and some full sun all day.

It sure does help to know what climate your cactus is native too.

[imafan26]

Move the plant out to where it will be in full sun all day. Usually by a building or wall it will get some shade and air circulation will be blocked. Your planter looks like it has the right soil. If you can find a clean section that is not infected yet you could start a new plant. It is hard to otherwise control fungal infections once they start. You can try baking soda as it is a dessicant and try to keep the plant out of the rain. One tablespoon baking soda and 1tablespoon oil in a gallon of water. Do not spray in the heat of the day the oil can burn. Try it on a small part of the plant first to make sure there is no phytotoxicity. I rarely spray cacti so I don't know how it will react . I live in a wet place but haven't really had a fungal problem and I do have dragon fruit. It likes to hang over the tile wall. In fact most places I have seen it, it is hanging over a fence or a wall, so I think it needs good air circulation.