Corrupting fever and support gems

Corrupting fever does not work with controlled destruction, despite being a spell. It works with brutality and efficacy.

It does not have the 'spell damage also applies to this skill's damage over time' modifier, spell is just a tag on the gem (eg: auras also have spell tag but they dont scale with spell damage). Dot's don't work with spell damage unless it specifically says that line in the gem description. Similarly, Efficacy will only apply its DoT component and not the spell part.

Reap/Exsanguinate has this line, and thats why those work.