How to wipe out a planet entirely?

I'm playing a Voidborne Hive. So I don't want to make use of the Devouring Swarm planet I'm about to conquer. Is there a way to make sure it's just wiped out?

Alternatively, I suppose I'm not THAT far off from Genetic Ascension so that I can remove the trait. And I am playing Lithoids. And it is the capital planet... So maybe I should keep it.

Still, what about the less developed planets?