Hi Barbarakeeter! Welcome to the forum!
First of all, before you get into treating anything, a few questions:
- how long have you had the rose?
- where did you buy the rose?
- did it have the split when you bought it?
- how big is this split, and describe it. (length,through the whole trunk, where on the trunk, etc.)
Send back all that information, and then I can better assess what you should be doing about your problem.