When did Ash's Palpitoad learn Sludge Wave ?

Question

In episode 9 of Adventures in Unova, Ash is battling Stephan and Palpitoad uses Sludge Wave wich makes Zebstrika Poisoned.When did it learn that move ?

Answer 1

It learns it in Strong Strategy Steals the Show!. BW106.

Source

Comments

so it has not used it before....