I started growing the tree from a seed. The sapling is about 12 inches tall.
You will prune after the tree reaches, roughly, the desired height. Then you can start the Bonsai process.
This collection of articles will help: https://www.gardeningknowhow.com/category/houseplants/bonsai
We live on the Tablelands near Cairns, and I have tried spraying the trunks with various products over the last couple of years. In desperation, I have partially painted the trunks with water-based household paint but the borers are getting worse. Drought here doesn’t help with the location of these trees and they could get stressed but we do water them when it’s very dry. We would hate to lose them after all this time, but we need help as to what to do next, please.
Unfortunately, once the infestation has progressed this far, it is hard to treat. Most of the damage has already been done, and since they reside inside the tree, treatment often doesn't help after this point.
Here is an article that will help you to attempt correcting the issue: https://www.gardeningknowhow.com/ornamental/trees/tgen/tree-borer-insects.htm