Reply To: Merlot on spurred cordon

[Piet]

Hello Tecla,

This is magnesium deficiency for sure. You can use some leaf fertiliser in summer. Did you take some soil samples last year? A surplus of potassium can also cause this.
Magnesium is mobile in the growing shoots, so you see the deficiency in the older leaves, it will be transported to the young leaves if they need it. So if you should spray, you must spray the young leaves.
Regards,
Piet