Last year I wrote that downy mildew was relatively uncommon in our vineyard. However, it has been cool and raining regularly since mid July this year, with another 3.5 cm last night and more rain predicted through the weekend. Ideal conditions for downy mildew.
And not too unexpectedly, there has been a lot of downy mildew in our vineyards this year. Not so much in the classic “oily spot” form, but in the much worse circumstance of significant leaf attack and vine defoliation caused by this fungus. I only spray with certified organic fungicide solutions. For powdery mildew this is sulfur, and for downy mildew the spray is historically copper sulfate. While there are other new and modern organic options these are not yet available in Hungary (more on that in a separate post).
While I always notice some small amount of fungus in the vineyard, regular spraying normally keeps fungus under control and with the ideal to avoid larger infestations. But organic solutions are contact fungicides, meaning they are only effective if they contact the fungus on a leaf or grape cluster. Rain will wash off the fungicide spray. And with this very wet year it has been a battle royal, as the below images demonstrate.