Barles wants to get rid of all the tumbleweeds in the trash heap that she found in Gerudo Canyon.
Quest Location
Talk to Barles at -1006, -3580, 0219 (east of Daval Peak) to start the quest.
How to Complete the Quest
Remove the tumbleweeds from the trash pit. There is a Flame Emitter partly buried in the trash that you can lift out with Ultrahand. Then hit the Flame Emitter and point it at the tumbleweeds to get rid of them quickly. There are also Fans that you can hold and point at the tumbleweeds to blow them away. Or you can hit them with your weapon to destroy them. Use whatever method you prefer.
Quest Reward
Barles gives you a Royal Shield.