Native Pest Of The Forest is a sidequest in Star Ocean: The Divine Force that can be picked up in Larcette Village.
This quest only becomes available once you have begun to fix Elena.
You can start this quest by talking to Undaunted Explorer just outside the Larcette Village Inn. He mentions that a dangerous frog is causing him trouble and wants you to help him out.
You're going to need to take out 2 Giga Toad mobs. These can be found in the Larcasse Weald towards the south.
Once you've taken out two of them, head back to the Undaunted Explorer to receive your rewards.
Rewards: