can't create a local mirror

[Tim Hanson]

I either have a problem with rsync or it is not intended to do what I am 
asking it to do.

I am trying to mirror a copy of /home/foo to a local usb drive.  The copy is 
made, but the destination does not appear to be deleting files I have deleted 
on the source.  Here is the command line I am using (part of a script I use to 
do this and other housekeeping chores):

As root:

rsync -av --progress --delete --exclude /home/foo/.local/share/Trash \
--log-file=/home/foo/Desktop/$(date +%Y%m%d)_rsync.log.usb$disk \
/home/foo /media/usb$disk

What am I doing wrong?