Weird growths on Gum branches

[u/mandalorian4]

My mum has this what I think is a lemon scented gum in her front yard which has these weird growths on the trunk and branches towards the canopy.

She had a lawn guy who was working on the neighbours house knock on her door and said the branches were dangerous and at risk of falling.

Any ideas what it could be? She’s making contact with a local arborist but would I’d like to get some feedback in the interim.

Thanks!

[u/Rude_Nectarine]

Previous drop bear nests?