PUEBLO, Colo. -University of Southern Colorado President Tito Guerrero announced this week that the USC wrestling program will be discontinued because of a  shortfall in the athletic department budget.    "I had to make a very difficult decision," said Guerrero. "I have reluctantly concluded that it is necessary to eliminate men's wrestling as part of the athletic program, effective immediately."     The move will directly affect nearly 30 student wrestlers and the wrestling coach, Doug Moses. The students' scholarships, which have already been awarded, will be honored for the coming year, said Guerrero.    "It was a difficult decision for me because the program has been very successful under the leadership of Coach Moses," he said.    Guerrero emphasized that budget problems within the athletic department made the decision unavoidable. USC must submit a balanced budget to the State Board of Agriculture next month.    "We basically have had an ongoing shortfall in revenues in the athletic department that we could not allow to impact our academic programs," he said.