Hi, I had questions several years ago about my Cereus Monstrose and you helped me then, so I hope you can help me now. My Cereus is quite large, over five feet. It has developed black spots on it which I am afraid are parasites of some kind. The first of these spots occurred last year and someone at the Jungle recommended putting Neem oil on them. This is not working. I cut a black spot out and the area turned black What should I do? I am very attached to this plant and I do not want to lose it. Do you make house calls?
It looks like the cactus has an infection, which is causing the rot spots. Probably viral which is difficult to treat. You treat with cleaning out the infected spots and sterilizing with hydrogen peroxide, and feeding the whole plant with kelp and neem.
We do housecalls, and if you would like we can come out and treat the plant for you. Please understand there is no guarantee we can stop the infection.