ltc.tbdice.org --scrypt is neccesary at command line?

[Photonic74]

Hi,
I am quite new mining.
I have a not powefull dualminer usb device and I am focus on 'lottery' issue.
The fact is that following web instructions --scrypt is not requiered in command line for bfgminer, and as far as I know is necessary for ltc.
Without --scrypt I have a ratio of 400Mh/s and with --scrypt it drops to 30kh/s and effective ratio is 0.
Any help is more than welcome.
Thanks