Take care of the needs of the Coronata Vineyard.
The Witcher 3: Blood and Wine - Wine Wars: Coronata
This quest is suitable for level 37 and up, like the rest of the ‘Wine Wars’ quest line. It’s automatically obtained when you complete the Wine Wars: Belgaard Quest, which can be triggered very early on in Blood and Wine.
When you activate this quest as your current objective, five markers will appear on your map. Each represents a ‘problem’ for the Vermentino vineyard. You’ve got to solve them. There’s no particular order to tackling these, so I’m just going to list them all in the order I found them:
Problem 1: Archspore Invasion
Quite close to Coronata proper you’ll find an Archspore Invasion. Take them down by avoiding their acidic spew and their root-based attacks, then destroy their nest by interacting with it afterwards. There’s no quest-crucial loot here, but the archspores do drop some semi-decent stuff, so be sure to grab it.
Problem 2: Persons in Distress
One of your waypoints will lead to a cave; clamber down and you’ll find a woman surrounded by three bandits. She’s been abducted from Coronata, and is their herbalist type. Kill the bandits, rescue her. When she offers to take you back to Coronata to sell you herbs, decline – if you say yes, you’ll be warped there, but you’ll want to loot the bodies of these bandits for some more clues as to the larger plot.
Problem 3: Even more Archspores
Eventually you'll come across an area with two archspores. Kill them, and use your Witcher senses to go looting. On a legless corpse you’ll discover a letter.
This combines with a letter found during the Wine Wars: Vermentino quest line to give a new clue, and triggers the ‘Wine Wars: The Deus in the Machina’ quest.
If you don’t have both letters, you can continue on to complete the quest line by simply cleaning up Coronata’s troubles and then turning the quest in, but far more interesting is to follow this deeper quest line – but that also has a much higher level recommendation, 42. Opening up The Deus in the Machina quest does not close this quest right away - if you discover this before your last 'problem', you can still go and clear out those that remain - just don't turn the quest in.
Problem 4: The lone Archspore
Another site, another Archspore. Kill it, Geralt will meditate, and it'll become a bustling location once again.
Problem 5: Rock Trolls
This site is based just the other side of a bridge - there's two nasty rock trolls. If two at once is too much, keep in mind you can fairly easily lure one away to isolate them. Kill them and you're done. Be sure to loot the corpse near the bridge - here, you'll find an item that triggers the 'Coin Doesn't Stink' Treasure Hunt.