Joe Petersen, the leading jockey at Delaware Park in 1985-'86-'87, has retired from riding and will join his family's printing business. In his final mount, the 35-year-old native of Garden City, Kansas finished fourth aboard Sey Mag Proof in the $20,000 Firecracker Juvenile Stakes, a six furlong event for 3-year-old Arabians at Delaware Park on Saturday, July 6. A 19-year veteran, Petersen's top victories came in the Denise Rhudy Memorial and Light Hearted Stakes last year, the Dover Stakes in 1995, the Caesar Rodney Stakes in 1992, and the New Castle Handicap in 1988."I have been riding 19 years now and I have become a little tired of it," said Petersen. "I really would like to try something else. I figure when you are tired of it, your head is not really in it. This is a very critical game where you have to make split decisions. I just feel that if I do not have my mind on it then I was not giving the trainers my best. It is just time for something new. I am going to go home and work with my brothers in the printing business. I am also going to work on my horse shoeing a little bit and slow down for a little while. My brothers gave me a part ownership in the printing business. I am looking forward to going home to Garden City in Kansas and being with my family."