Question
QUESTION: I have a 5 year old brain cactus cutting from a very large brain cactus from Florida. It was doing fine for years until i moved and it got scorched in the car one day. After that it got real sick, some parts fell off and it recovered. At the new place it got some kind of infection that turned half of it yellow and mushey. I cut that part off, repotted it and it recovered. Now all of a sudden the top is turning yellow and that part has all these little black spots spreading all over! This cactus has sentimental value as it was a gift cutting from someone who is no longer alive, please help if you can! This is the kind of brain cactus that doesn't have alot of spikes on it. It is the kind that has two different shades of green that swirl and make patterns on the pads, but it isnt the kind that usually shaped like balls and covered with yellow spikes.

ANSWER: Hello Chris,
Due to all that repottings and cuttings, you were probably motivated to do the mistake that everyone has made...Overwatering! The yellow parts of your cactus was most likely due to the overwatering. You should always let the soil dry completely between waterings, especially when a plant has been injured. This is because the moisture develops bacteria and fungi that will continue to attack your plant. That probably explains the black stuff! If you want to save your gift, don't be fooled by the way the cactus looks thirsty. Allow the soil to dry. Cactus are succulent plants, which means they tolerate droughts. They take advantage whenever there is water available. So the plant would drink and drink until it starts to rot. Please let me know if you have further questions.

---------- FOLLOW-UP ----------

QUESTION: Thanks, I cut off the really bad parts on the top, bought a new pot. Filled it with 50/50 cactus soil and vermiculite prevent the soil from holding too much water. After the bad parts were cut off I rinsed the whole plant in a 10% bleach solution to sanitize it and then rinsed it clean. I repotted by holding the plant at the level i wanted and pouring the soil mixture around so that it filled between the roots as they had become accustomed. I found the old original main root (about an inch in diameter) that had died when it was scorched years ago. The main part of the plant that I didn't cut off deadened the roots and sprouted a whole new system! Guess that's why it had been growing slowly. With new, clean, dry soil the plant seems to be recovering quickly in only two days! The wounds have already almost closed up! Thank you so much for your help. Please let me know if there is anything else I should be doing from this point. When i opened the soil I did find there were some small flying bugs living in it and I noticed that the more developed black circles were surrounded by little black bumps. Dont know if they are related, but their gone now.

Answer
Hello Chris,
I'm delighted to hear from you. I'm also delighted that you removed the bad stuff. The only thing you should do now is:
Don't overwater anymore (wise decision about repotting).
Continue removing rotting parts to prevent fungi again.
And finally, enjoy your plant!