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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 '18 at 17:01
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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... – Julia Correcher Apr 7 '17 at 16:20
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This is how is looking after the intervention, any ideas what is happening?enter image description hereenter image description here

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    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 '17 at 17:25

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