Pichu is not a wild Pokemon that can be found in Ilex Forest. You can obtain Pichu through the following methods:
* Breeding: You can breed a Pikachu with another Pokemon to have a chance of getting a Pichu.
* Trading: You can trade for a Pichu from another player.
* Events: In the past, there were events where players could obtain Pichu.
While you might find information suggesting Pichu is in Ilex Forest, it's likely outdated or referring to a different game.