When it's "ready" you'll notice 'root buds' beginning to grow in sort of a halo around the base of the big bud. You can plant it right now in *slightly* moist soil- But don't water it at all untill it starts to grow. WHen it does, you'll know.

leave the tip pokin' up a little if you want- easier to see it growing, but once it does bury the whole thing under a few inches of dirt.

Konjac is about as easy as it comes with amorphophallus.

What you might want to do is dab the area that molded with a bit of diluted rubbing alcohal .. and then let it dry just to make sure everything is nice and dead.

Like Krstofer said you may want to wait til you see root buds forming on the base of the shoot.

I dont know what your growing conditions are, but I know here in seattle we are still mildly cold and rainy..Someone gave me a tip about actually starting the bulb in a pot indoors. plant it about 2 inches down and give it just enough water to make the soil moist not wet.. and wait til shoot breaks the surface.. then put it outside in a nice sunny spot..

Chris