Disease Identification

[Xnke]

Anyone got a diagnosis for me?

These vines are at least 50% malbec, and may be 100% malbec. They are not showing the same traits as the mother vine did, however these are only a few months old.

Only leaves that have grown long enough to loose the dark bronze coloration and turn green, are affected. Older leaves are not affected as much, or at all. The vines get Mancozeb mixed with Sevin about every two to three weeks, depending on weather but that will stop soon and I'll have to switch to Captan due to PHI limitations.

 

[balatonwine]

My first impression would have been downy mildew. But since the vines seem to be protected from surface diseases by spraying, and due to the curling, my next thought is either nutritional, or eutypa dieback, or spray damage (young shoots can be sprayed too much and get burned by some chemicals).

 

[VinesnBines]

Leaf curl is tough to determine the cause. Insect, chemical, or environmental (heat, drought). If no galls or aphids, think about chemicals (herbicide? spraying on the heat of the day? hot winds or grow tube burn?). I’m thinking mine is grow tube burn. I’m hoping.

 

[Xnke]

Since we are coming up on the dry season, and the Japanese beetles are just about done, I'll hold off on the sprays a bit and see if they are just getting over sprayed or are sensitive to the spray mix. These vines are in their first growing season, and one of the two is the one with the badly healed graft.