wu-ftp - name resolution and delay

hi all

someone could help me in a wu-ftpd specificity : name resolution

when i try to connect on my wu-ftp server
i get big delay :
    ste@quarantaine:~$ ftp jpl
    Connected to jpl.
--- big delay
    421 Service not available, remote server timed out. Connection closed

with tcpdump -i eth0 | grep -v ssh
i can see PTR request :
    15:11:52.552377 10.10.10.17.2083 > 194.2.0.50.domain:  39636+ PTR? 
49.200.9.192.in-addr.arpa. (43)

wu-ftp try to get the name that goes with the adress 192.9.200.49

when i move a line in nsswitch.conf to remove dns in host line
i get better delay : i can connect ,but the delay is still here

when i rip off name servers from the /ets/resolv.conf file
i get no delay as i expect it

I would like to know how I could make wu-ftp not trying to resolve the 
name (as i don't care)
without deactivating all the name resolution process widely (nsswitch 
and resolv)

thank you much in advance