Mai says there is a massive mass outbreak in the Coronet Highlands and asks you to investigate.
The Request
After you complete Tricky Treat Strategy, this request will begin.
Investigate Massive Mass Outbreaks
Talk to Mai if you want to feed Munchlax some Aguav Berries to reveal the massive mass outbreaks on the map. As before, catch or defeat all of the pokémon at a massive mass outbreak to clear it. Repeat this until you have cleared three of them. If you take too long and the massive mass outbreak ends, go back to Jubilife Village, then go to any area outside of the village, and keep going back and forth until another massive mass outbreak occurs.
Report to Mai
Go to a base camp and talk to Mai. You will get 100 Spoiled Apricorns, 100 Balls of Mud, and 100 Caster Fern Leaves.
Reward
For completing the request, you get 30 Apricorns, 30 Tumblestones, and 20 Balls of Mud.