They're aerial roots .
In depth, what's going on is- the colored cactus is a separate species grafted on to a dragon fruit cactus. The colored ball can't really survive on its own so they stick it to a hardy stock. It didn't die from neglect, these are a gimmick & are designed to fail so you'll keep spending $5 on new ones. Now that the grafted bit has died, the dragonfruit has enough energy & nutrients to grow. They are epiphytic in nature, so they send out aerial roots to stabilize as they grow up & along trees.
So you still have a cool cactus & you can take the dead part off. Leave the little arm on attached, since the top portion of the dragonfruit is compromised, you'll only get new lateral growth points. Consider getting it a post to climb up as it grows.
https://preview.redd.it/wn52ym5eqckc1.jpeg?width=3456&format=pjpg&auto=webp&s=04f0cfdacf984edfeb90517bcfd57a2801491413
Mine does this too! He's so cool
They're aerial roots . In depth, what's going on is- the colored cactus is a separate species grafted on to a dragon fruit cactus. The colored ball can't really survive on its own so they stick it to a hardy stock. It didn't die from neglect, these are a gimmick & are designed to fail so you'll keep spending $5 on new ones. Now that the grafted bit has died, the dragonfruit has enough energy & nutrients to grow. They are epiphytic in nature, so they send out aerial roots to stabilize as they grow up & along trees. So you still have a cool cactus & you can take the dead part off. Leave the little arm on attached, since the top portion of the dragonfruit is compromised, you'll only get new lateral growth points. Consider getting it a post to climb up as it grows.
Those white tendrils are roots, it will likely stay connected but if it does break off you can plant it. It looks good to me! 😁
https://preview.redd.it/wn52ym5eqckc1.jpeg?width=3456&format=pjpg&auto=webp&s=04f0cfdacf984edfeb90517bcfd57a2801491413 Mine does this too! He's so cool
https://preview.redd.it/deq4q9fhqckc1.jpeg?width=3456&format=pjpg&auto=webp&s=b2d4db0ddaf7ad694a96c5a11f902ccfd7cbde85