Food chain

[Maxpayne03]

Can {Pithing Needle} Stop {Food Chain}?
It is a mana ability?

[Kaylesh]

Can {Pithing Needle} Stop {Food Chain}?
It is a mana ability?

Is it a mana ability?
That boils down to two things really?
Does it create mana? Yes.
Does the ability that generates the mana target? No
In that case, we have ourselves a mana ability.
So, {pithing needle} won't stop this.

EDIT: turns out I forgot one.

605.1a: An activated ability is a mana ability if it meets three criteria: it doesn't have a target, it could put mana into a player's mana pool when it resolves, and it's not a loyalty ability. (See rule 606, "Loyalty Abilities.")

So, if a planeswalker would use an ability to generate mana ({Koth of the hammer} for instance), it is not a mana ability, and will use the stack, can be responded to, and will be stopped by Needle.

[Maxpayne03]

Since it's a mana ability, do I get to activate {Food Chain} when my opponent {Krosan Grip} It?

[scarsabrex]

Correct, which means you could potentially morph say {willbender} or {voidmage apprentice} in order to save your food chain.