Greetings Debra:
You have four options depending on the size of the trees in question: (1) cut stump treatment, (2) girdle or frill, (3) basal application, or (4) foliar application.
Seeing that this particular species is not listed on the majority of the more familiar woody herbicide specimen labels AND that this request is coming from outside Illinois, I must direct you to your state's forestry agency.