It does look like mildew. Any way to clean it off or just let it dry out? Actually, that's called "sooty mold", and it's a problem when we're growing some Opuntioid species in a humid environment. Good news is that sooty mold is a bit unsightly, but by no means life-threatening. The humid...

I have had this San Pedro for about two years. I have to admit I neglected it the first year but have become a better cactus parent in the past year. It sits outside in the sun from morning until probably around 3pm every day. I suspect its not gotten enough water but am wary of over watering. My qu...