Rubinea Tree

I have a lovely Rubinea Tree which has a similar complaint, I think, to one already described by another user. It has been displaying a lot less foliage for the last few years and is clearly not very healthy any more after several lush and healthy years.
It has a large gap in the trunk and may have the same complaint, i.e. a trunk grub of some kind. Any ideas of what I can do to save it?

 

Have not seen post you are referring to but surely you are asking about Robinia.

 

Ron, I think it may have been this, that I posted on a previous thread,that Doune is referring to.

http://www.rhs.org.uk/advicesearch/Profile.aspx?pid=401

 

Was not sure if I saw that here or elsewhere. Not enough information to tell if same problem. Do need to find out what is wrong with the tree before useful measures can be taken.

 

Thank you for your response. I shall try to organize a couple of photos for you to see.