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My cactus has this brown areas growing across the surface since a week ago. If you try to remove them, they are like a hard skin that comes off, the surface underneath is normal green color but appears a bit wet. What is it and what can be done?

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  • It's not a bug infestation because those are a brighter white color and fuzzy. I've had them on my plants before. This is something else. More likely a disease.
    – Johnald
    Apr 19, 2018 at 17:01

4 Answers 4


I suspect it's a scale infestation - cactus plants, if damaged by anything (insects or physical damage) develop corky areas exactly this colour, but these look bumpy, so I think they're probably scale insects.

You can try manually levering them off, but the damage beneath will likely turn into corky patches,, the cactus equivalent of a scar - even so, you do need to treat the problem or it will get much worse. Some cactus don't respond well to insecticide treatments, and most of those treatments don't penetrate the adult scale anyway. You could try using a cotton bud dipped in rubbing alcohol or methylated spirits, dab the scale insect and then try lifting it off, but don't get the spirits on the plant itself. Cover the soil before trying to remove the scale, because you don't want reinfection to occur.

More information here, including advice on removing the scale http://www.desertplantsofavalon.com/how-to-remove-scale-from-cactus-plants/

  • Unfortunately no scale insects, I removed the brown areas and they have turn black. The situation is getting worse as the cactus is even changing form... Apr 7, 2017 at 16:20

This is how is looking after the intervention, any ideas what is happening?enter image description hereenter image description here

  • 1
    I can't see its growing differently, but clearly it hasn't responded well to removing those growths. Since there doesn't seem to be any other infection present, I suggest you just leave it alone and see what happens next, but something caused those scabby areas to form - its possible whatever it was has now departed, but see what happens over time.
    – Bamboo
    Apr 7, 2017 at 17:25

Im pretty sure you have a bad mealybug problem that’s why 95% of the areoles on your cactus are covered in white clustering fluffy stuff (mealybugs). You should be able to remove them by blasting them with a spray bottle, the pump-up bottles work best. Also use a couple drops of dish soap in the water to ensure and stragglers die! If this doesn’t work use a 50/50 water and rubbing alcohol mix and dab and twist them off. Once you have removed all the visible white stuff (mealybugs) with these treatments, water your cactus (only when you normally would) with a couple drops of dish soap shaken up again, leave for a good 10 minutes and water again with fresh water to rinse. Mealybugs can livi in the soil and at the base of the pot its best to have sterile environment.

  • Welcome! I am pretty sure that the white “fluff” is perfectly normal, lots of cacti have it. Please note that the question is about the oval patches, not the area around the spines. One of the rules of all SE sites is “answer the question” and unless you are talking about the patches, this technically isn’t an answer and will be removed. The tour and the help center will explain more about how the site works.
    – Stephie
    May 6, 2020 at 12:10

I have a Myrtillocactus cochal that has the exact same pattern of disease. I've been told that it is a fungus. I have tried everything and nothing has stopped it. We'll see this season if it will infect the new growth of the cactus.

Disease on cactus. The bottom part is where I tried about everything on it.

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