We have just built a new house near Bendigo, Victoria. My son bought me a beautiful Eucalyptus tree (Sideroxylon rosea), which I planted, keeping in mind that it will be big. I got the tree for Christmas and planted it within a week. It is growing well except it has ants (approximately 1 cm in length) climbing up and eating it. They do not have nippers; they are not leaf cutters. But they appear to be the cause of my diminishing gum. All the lower leaves have gone! Have you heard of this? There are no pests around. Have I perhaps planted near a nest (I can't see one)?
Gum Tree Diminishing!!
Certified GKH Gardening Expert
It is probably not the ants that are taking the leaves but rather aphids. Aphids attract ants (which keep them like we keep cows for "milking") and this is probably why the ants are going up the tree. The aphids are very small and you may have missed them, but they can cause leaf drop. Treat the tree for aphids and the ants will leave too.
These articles will help: