You need to get rid of the ants and then take care of the other bugs. The ants are farming them for their juice that they are sucking from your tree. Same for aphids and scale. You have an ant problem first and foremost.
Use tangle foot on plastic wrapped around the trunk to stop them and get some ant bait.
Thanks Brad. I already did, ants are gathering around without find the way to come back home. I found the species of mealybug too, is
Icerya purchasi if I'm right. It has a predator, the beetle
Rodolia cardinalis, I think I saw one yesterday over one of my pitayas. I removed all the leaves affected that I found and sprayed some Potassium soap. Just found 4 adult females, so it seems at the first stages of the process, I'll check again tomorrow. If I find more Rodolia, I'll move them to the tree.