Unable to see the results of /check-netapp-ng.pl Disk Used

I can able to see the results of disk used details
./check-netapp-ng.pl -H 172.16.4.16 -C public -T DISKUSED –vol /vol/vol_testlab/
OK: DISKUSED 1% | /vol/vol_testlab/= 23365520k

However i couldn’t get the results for below query, correct me if im wrong.
./check-netapp-ng.pl -H 172.16.4.16 -C public -T DISKUSED –vol /vol/vol_testlab/qtree_testlab
|
NO RESULTS DISPLAYED….

I couldn’t get the subfolder disk information from this plugin. let me know how to get those details..Thanks in Advance!!