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Q.White Spots On San Pedro Cactus

Zone Tehran | Amertat Rad added on January 12, 2021 | Answered

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.

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Certified GKH Gardening Expert
Answered on January 12, 2021

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:


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


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Answered on January 13, 2021

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.

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