# pfctl -t intruders -T show|grep 192.168.1.11
   192.168.1.11

# pfctl -t intruders -T delete 192.168.0.0/16
0/1 addresses deleted.

# pfctl -t intruders -T show|grep 192.168.1.11
   192.168.1.11


The delete command is straight off the pf user's guide under, Manipulating with pfctl
http://www.openbsd.org/faq/pf/tables.html