Hi, I have a Catalpa tree that is at least 20 years old. I have noticed over the last couple years that during the summer one side of the tree towards the top looks like someone has sprayed it with a plant killer and the leaves start to curl, turn yellow and fall off. It also has a lot of little branches growing straight up on the older branches that are larger. I had a friend say that the little branches are suckerlings and is the trees last attempt to try and survive but it is dying. Is this true? Is my tree dying? How long will it last?

From your description, there has been damage to the one side from an unknown cause. The suckers are likely created just below where the damage is located as the tree has the energy with no place to go. The tree is not necessarily going to die if the damage is limited to one branch and the rest of the tree is growing normally. Finding out why that branch has died will aid you in determining the next steps. You should contact your local Extension office and or an arborist to get a locally focused answer.