bark is coming off our 15 metre silver dollar gumtree
Is this okay? Big pieces of the bark are coming off. Little beetles are underneath. Is the tree sick?
Here is an article on eucalyptus trees. https://www.gardeningknowhow.com/ornamental/trees/eucalyptus/tips-growing-eucalyptus.htm
A certain amount of bark peeling may be natural for your tree. Here's another article on peeling bark: https://www.gardeningknowhow.com/ornamental/trees/tgen/repairing-tree-bark-damage.htm
You may be able to clean and repair; however, it would be to your advantage to find out the cause of the bark peeling and the beetles. The insects could be eating bark, or they could be feeding on some kind of viral of fungus infection. Try collecting some bark and bug samples, and getting them analyzed by a university department or registered arborist.