Why not setup exterminatus traps aganist Tyranids?

Instead of destroying the entire planet (before the invasion starts) in order to starve the hive fleets (even Dante did that) why not setup a trap and lure them to the ground then do the Exterminatus. It can be done as a tactic to slow them or as a last resort after failing to defend.

As a result the fleet is deprived of its bio-matter plus lost a lot more because most of its forces were on the ground when it blow up. I know that Tyranids can harvest both the living and dead (theirs too) but surely not a cooked planet.

Edit: Thanks for the comments I think I need to make myself more clear:

https://www.youtube.com/watch?v=VAM8qUIGr1U

Is such a weapon only be deployed from space? Cant it be buried underground to go off if all other options fail? I am not talking about virus weapons no I am talking about the planet burning cracking type. Also I have seen exterminatus deployed even on populated worlds too even Dante did that to slow the Tryanids advance.

Edit2: Thank you soo much for the all comments,upvotes also downvotes and negative arguments too. The reason we have reddits like this is to discuss.