dredge and pithing needle

[BigMac]

Could pithing Needle stop dredge of a certain card. Or for that matter, could pithing needle stop a creature ability that would bring it from the graveyard back to play like Ashen Ghoul or Nether Shadow.

[UR]

I believe that it can't stop dredge because it isn't activated (it is triggered I believe) but it can stop cards in the graveyard such as Ashen Ghoul. It reads;

Haste
B: Return Ashen Ghoul from your graveyard to play. Play this ability only during your upkeep and only if three or more creature cards are above Ashen Ghoul.

So it is activated and can be stopped.

Nether Shadow is again triggered and won't be stopped.

[Khahan]

Could pithing Needle stop dredge of a certain card. Or for that matter, could pithing needle stop a creature ability that would bring it from the graveyard back to play like Ashen Ghoul or Nether Shadow.

[card]pithing needle[/card] shuts down non-mana activated abilities.
Dredge is a replacement effect and not affected by pithing needle.

The effects of [card]ashen ghoul[/card] is an activated ability and can be shut down by needle. [card]nether shadow[/card] is a triggered ability and not affected by pithing needle.

If you ever have a question about an ability, think of pithing needle as reading: Name a card. If an ability of that card has a ":" ni it and its not a mana ability, you can't use it.

[Khahan]

I believe that it can't stop dredge because it isn't activated (it is triggered I believe)

Dredge is a static ability of a card in the graveyard that generates a replacement effect. Its neither activated nor triggered.