Damage+20% vs xxxxx for staff?

Now I want to know if a Damage + 20% vs xxxxx for staff, only affect the staff or everything the user does.

Exemple:

Staff of Prunning (20%)
When I'm up against Plants where does the 20% more damage applies?
To the Staff damage (11-22)?
To the caster damage? (lets say an Elem who casts Fireball)
To both?

Because, I don't see the point of having such an upgrade if the damage only applies to the staff damage.

Thank you!

Pretty sure it only effects staff damage. Although, I have never bothered to test it myself.

Oh, and there's also no good reason that req 13 soul reaping HSR Divine Favor HCT Energy Storag staves of Illusion Magic drop in PvE. Never the less, they still do drop in PvE, all too often... ANET is not always logical.

I would guess it only affects damage, but if other mods like poisonous affect spells it might be worth testing to make sure.