Walkthrough for the side quest Wine Wars: Coronata from The Witcher 3's second DLC expansion, Blood and Wine

Walkthrough

There are five problems to solve, each with its own objective marker.  If you start from Plegmund's Bridge, and do them in the order suggested by the game map, then you encouter:

1. Vineyard Infestation - Archespores.  Use Cursed oil, Aard and/or Igni.  Destroy the monster nest to complete the objective.

2. Guarded Treasure - Archespores.  After disposing of them examine a body to find "Orders on Elegant Stationery".  On reading the letter several outcomes are possible:

• If you did Wine Wars: Vermentino before this one then you already found a similar letter and automatically receive the level 42 quest Wine Wars: The Deus in the Machina.
• If you rejected Matilda's request for help during Wine Wars: Belgaard (L37) then you automatically gain the quest anyway - Wine Wars: Vermentino.
  BUT, if you complete this as the LAST of the five objectives then you do not receive the Vermentino quest or The Deus in the Machina, and your only option is to turn in this quest.
• For Wine Wars: Coronata (if you have the Vermentino quest) you receive an option to search Vermentino and find proof of sabotage.  Choosing this option does not result in a new objective marker.  Thus it is better to pursue Wine Wars: Vermentino and gather the evidence you need to trigger the quest Wine Wars: The Deus in the Machina.

3. Abandoned Site - Archespores.  There is only one but there may be several other foe markers for child spores.  When the main plant goes down then the people will return to the site, completing this objective.

4. Hidden Treasure - Rabid rock trolls.  Use Ogroid oil and Quen. After dispatching them check the corpse at the east end of the bridge to find "Letter to Cosmo Cyrille" and a key to a lockbox.  Reading the letter adds the Level 37 Treasure Hunt "Coin Doesn't Stink" to your jounal.  Search the area around the bridge for some miscellaneous loot.
On your way to the last objective you can find the Trading Post travel marker by the cluster of three buildings southwest of the objective marker.

5. Person in Distress - Bandits.  There is a cave entrance in a ravine northeast of the marker.  Inside are three bandits holding the Coronata herbalist hostage. Slaying the bandits starts a scene with the herbalist where you have two conversation options:

• "Let's go" - nets you an instant trip to the Coronata vineyard.  If you don't have the travel marker yet then go southeast of the complex to a fork in the road.  You can also finish Coin Doesn't Stink at this point.
• If you end the conversation instead, the herbalist will leave and you can search the cave for loot.  One object of interest is the "Dirtied letter" with instructions for the bandits about the kidnapping.  Reading it does not advance the quest or give any new quests.
  

a. If you want only Liam to own Belgaard and have not completed any Vermentino objectives then return to the Ducal Clerk at Plegmund's Bridge.  Matilda is crushed, and will not appear at Belgaard.
This quest ends and you receive the next quest Wine Wars: Belgaard (L39).  Your 100 XP and whatever fee you negotiated with Liam are paid after the opening scene at Belgaard.

b. If you completed this quest after Matilda owns Belgaard, return to Liam and let him know his vineyard problems are over.  You receive 100 XP and your negotiated fee of 700 gold or more (or 525 if you did not negotiate).  The quest ends.
There are other options for ending the Coronata/Vermentio quests.  They all begin by starting a conversation with the Ducal Clerk at Plegmund's bridge.
If you have not completed Wine Wars: The Deus in the Machina -

c. If you have completed all objectives for both of those quests then you can say, "Both vineyards should be fine now".  The Clerk forces a partnership on Liam and Matilda, and neither is happy about it.

d. If you report sabotage at both vineyards you can still play out (c).  But it's better to end the conversation now if you want XP for doing Wine Wars: The Deus in the Machina.
If you have completed Wine Wars: The Deus in the Machina -

e. You report the saboteur's identity.  Liam and Matilda are surprised to learn that neither of them was responsible for the sabotage and gladly form a partnership.

1. If you completed all the objectives for both Wine Wars: Coronata and Vermentino then, at the end of the conversation you can agree to go to Belgaard or end the conversation. Your rewards for those quests will be received when you visit Belgaard.

2. If there are any uncompleted objectives for the Coronata/Vermentino quests you gain the level 40 quest Wine Wars: Consorting.  Your rewards for the Coronata and Vermentino quests will be received when you turn in Consorting at Plegmund's Bridge.

Either way, Wine Wars: The Deus in the Machina ends and you recieve 250 XP.