Root mealy or leaf/surface mealy? If you have the latter, there's no connection between the soil and the bug. If the former, I'd bake it.

Root mealy, unfortunately. How long do you bake and at what temp?

Thank you!

I don't know what temp you have to reach to get rid of root mealy eggs and such. I would think boiling would do it. Baking in the oven will only get you to boiling temperatures until the medium dries out then you can hit those higher oven temps. Another option would be a pressure cooker at 15# pressure for 45 min. That is essentially an autoclave and will get you pretty damn close to truly sterile. I like wet sterilization just so I don't have to run into hydrophobia issues.

nil13, thank you for the suggestion. Does boiling break down the mix at all? Unfortunately I don't have a pressure cooker, that does sound like a good idea.

Okay, now I am a bit confused. I just beheaded the plant (well, the mealy bugs basically did that for me as it just snapped off of the rotted stem in the soil) and I can see some very small mealies in the nodes of the leaves on the plant. So, clearly they were working away at the plant at the roots, but what were they doing on the upper part of the plant? Does that mean I have both types (root and plant) mealies?

Correct - one can have either or both, but they're not related to each other (different genera).

Just my luck! Thank you for clarifying that for me :)

I'd imagine if you boiled it in water it would do the trick for the root mealy (and for the surface mealy, but the plants wouldn't much like it), just spreading the soil a little to dry out for a few days and Bob's your uncle, you're ready to repowder your shells, as it were.