White Spots On San Pedro Cactus

Question

Hey guys. My friend gave me a san pedro cactus last month and I’ve prepared most of the growth conditions it requires, but about a week ago, a somewhat large white spot appeared on its stems and now it’s spreading. I searched for pictures of San Pedro’s infectious diseases but nothing resembled the white splotches on my cactus. I touched the spots as to maybe find out what they are, it seemed like they had a powdery texture. If it’s any help, I haven’t watered it much since it’s winter, the indoor temperature of my house is usually 25°C. I’ve placed it behind my south side window and I believe it gets sufficient sunlight. Any help would be much appreciated.

Answer 1

This is most common with previous overwatering. It is good that you have cut back, but it may be necessary to treat with a fungicide. Otherwise, once the conditions are more favorable for the cactus, the scabbing will subside.

Here is an article that will help:

https://www.gardeningknowhow.com/ornamental/cacti-succulents/scgen/cactus-scab-treatment.htm

Here is an article that will help you with fungicide use:

https://www.gardeningknowhow.com/garden-how-to/info/using-fungicides-in-garden.htm

Answer 2

I can't thank you enough. This is my first attempt at caring for a plant I was genuinely worried I was going to ruin this amazing cactus. Although I'm still a bit concerned about using a fungicide. I read the links you posted but I don't know which type or formula is best in my case. I'd appreciate your help on that.