Black Spot on my Cactus

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Hi Cactus Jungle,

May I ask, do you know why this cactus body is become black spot?
I just bought my plant last week. Yesterday I clean the brown patch (dead scale) from the cactus body.. However, the spot that I clean become black spot.. Today I tried to clean that again and scratch & wipe it using alcohol. However the wound is turn to black again.. Is it normal? Is it a disease and can it spread to next plant? Do I need to repot the plant?

Close-up of a green cactus with a round, dark hole—possibly a black spot from plant disease—in its surface. Other cactus plants and a black pot appear blurred in the background, emphasizing the unique texture of the cactus skin.

Close-up of a green cactus stem showing several round brown scars and small white areoles, with visible surface texture. Natural sunlight highlights areas while others remain in shadow—signs that may indicate cactus disease such as black spot.

Thank you very much for your help.

Regards,
Cynthia

Cynthia

If there was scale there then the insect caused some damage on your cactus and it can take some time to heal. However, it sounds like you scratched it off and are still scratching at it. That is damaging the plant in itself. At this point you need to worry about rot and fungus, so I would recommend spraying with an organic neem oil.

In the future, spray the rubbing alcohol to kill the scale and let the remnant shell break down before cleaning it off with a soft paintbrush.

Peter

    
    
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