No. you can still use AF but you need to 'feed' the AF with something contrasty. As mentioned above, you can use a torch light or the AF assist (either built in flash or red beam of external flash). You could also focus on something at about the same distance, lock the focus, switch to MF and recompose. But please check your aperture and the resulting Depth of Field. Shooting wide open will likely result in misfocusing if the distance is not exactly matched.
Doesn't matter.
