Q.Myer lemon tree
I have some black looking bug type things on the leaves and branches of my tree. They are difficult to remove, I had to scrape them slightly but I can not find out what it is. The tree is approximately 3 years old and I have had two small crops it looks very healthy apart from some of the leaves that have been eaten by wallabys.
Certified GKH Gardening Expert
This could be a type of scale, or mealybug. It would help to have a picture for identification. There are a few things that you can do to help smother them, though. Neem oil is a good way to do so, as long as you do not apply in direct sun.
This set of articles will give you more ways to control insect issues: https://www.gardeningknowhow.com/special/organic/