Hi @sbrown50,
Thank you for your question and welcome to the Bunnings Workshop community, it is fantastic to have you join us.
I'm so sorry to hear that borers have gotten into your lemon tree, especially as it's such a well-established tree.
If you could upload some of your own photos that would help our members to offer their best advice. Let me know if you need some assistance uploading images, I'd be happy to help.
Were you referring to the photos in this discussion? How to kill borer beetle in lemon tree?
If so, the advice would be similar in that once they're in, it's nearly impossible to save the tree. You could try to use methylated spirits, pyrethrum or physically removing the borers but if they've laid eggs, it's likely it's already too late.
It might be best to contact a pest control specialist that is local to your area. You can find a pest control specialist using a service such as HiPages or True Local.
Let me know if you have any further questions.
Jacob
