Insects do not want to get wet. They want to live in dry cavities. Dead zones within the soil are good habitats for colonial insects such as ants, aphids, termites and other bugs. Within the dead zone they dig tunnels and caverns in which they could dwell. Air pockets within dead zones are instant habitats. If you see ants roaming around your leaves and branches the next thing that would follow are aphids. Aphids by themselves do not walk around they rely on ants to bring them to the juiciest parts of the tree. Aphids suck the tree’s sap and in return they feed the ants with their sweet body secretions. Aphids are like cows to ants as cows are to humans. We take care of cows so that we get constant supply of milk. So the ants herd the aphids like humans do to cows. If you see ants, then you have a dead zone. The best away to avoid the subsequent aphid infestation is to repot immediately. Make sure of course that there are no dead zones or air pockets or the ants will just come back. Try a different soil mix.