Hi - could anyone help with this brown colour that's appeared on my cactus? Not sure if it's something wrong/to be worried about and if so what can be done. Seems to be mostly confined to the spot shown in the picture at the moment. Thanks!!

Its either scale insect or sunburn

Could It maybe corking or root rot? Worried about the second one.

Added a second pic. Thanks!!

I'm not quite sure what's going on. I've never seen anything like that on my plants.

It does not look like sunburn to me, for 2 reasons. Indoor cacti basically cannot be sunburned unless they are coming out of deep shade (indoor sun lacks most of the UV component of outdoor sun), and sunburn tends to have a distinct spatial orientation on the surfaces of the plant that were facing the sun. It also does not look like scale insects, unless this is scarred tissue from a previous scale infestation. Individual scale bugs are actually pretty easy to identify (under magnification if necessary) and mature ones tend to sit down on the stem in a way that makes removing them (with the sideways motion of a toothpick or similar tool) straightforward. If there are small round raised areas on the stem that you can dislodge, that's scale. If not, you might be witnessing their aftermath, or likely something else.

Hopefully someone else here will have some better ideas.

Somehow it looks like effect of poor air circulation around your plant. Does any of the brown area feel soft?

I see that condition if plant got too humid at one point, then it calluses off.

I do agree it is hard to sunburn them indoors..so I think it is watering/humidity issue. These plants prefers warmer and drier. So it will lead to that brown scarring surface if environment keeps getting humid. I hope your media is very porous and well draining, otherwise basal rotting might soon occur.

I will recommend to check the root system, I have 1 fairy castle that grown something similar to that, those brown stuff only grown on the outer layer of the cacti, the plant also stop growing and somehow shrink. Below is the current situation, last month I get rid of more than 10 branches that seriously damaged.


This morning I repot the plant, the roots still exist, but I have a strong feeling that it should at least have a root ball that is triple in size, I checked the soil, there are some very small white bugs moving around, very small and difficult to see them without black color background, not very sure whether they are the cause of the problem, anyway I just change the soil with a new media.

And last month when I get rid of the damaged offsets, I kept and root 1 pcs that had less damage, and today it grows very well, that's why I suspect there may be some damage on the root system of the mother plant


Another parameter to consider, normally I water all my succulents with ground / rain water, just a couple of weeks before I had this problem, I watered the plant with water from the koi pond ( assuming that the water from pond will have more nitrate for the plant), this pond water may have brought in the parasites or something that damaged the roots of this plant.