how to trim off text

I have a varchar2 column have data like below: 001
002
003-ABC
004-XYZ
005

I would like to trim off everything after '-', resulting in 001,002,003,004,005. How do I do that? I tried rtrim but it looks like it can only trim off a fix value of text..

Thanks in advance,
Susan Received on Fri May 23 2003 - 13:17:13 CDT