I have an outdoor cactus; it recently developed an ant problem and they attacked the new growth causing what looked like sick spots

Question

on, what do I do? This cactus was doing so well growing and bringing such beautiful color to the garden.

Answer 1

There was probably an injury at the top due to insect, animal or mechanical activity. The secretions probably attracted the ants. You can try excising the sick looking spot. Here is how:

https://www.gardeningknowhow.com/ornamental/cacti-succulents/scgen/cactus-going-soft.htm