DeChaunac spring shoot tip die off

[user 36973]

I put in a couple hundred DeChaunac vines a couple years ago. Of the 13 varietals growing in my vineyard, this is one of the more peculiar.

In the spring it buds out fine and seems to produce an large quantity of flower clusters. Sometime around bloom the plant is beset by some sort of die-off of the shoot tip. It browns, curls up and takes the cluster with it. Last year I had blamed a spring frost for it but as it happened again this year, I'm looking for another answer. Wish I'd taken a picture of it in June.

The usual suspects of downy, anthracnose or black rot have been absent in the other sensitive varietals I'm growing, in spite of the frequent rain this spring. So this gives me some confidence I sufficiently timed the mancozeb/rally sprays this spring & early summer for the vineyard.

Is there something else that DeChaunac is particularly sensitive to that needs to be addressed to prevent this early season issue from returning?

 

[bshef]

Could it be spray damage? DeChaunac is slightly sensitive to sulfur. It really sounds like some sort of deficiency. Maybe you should try petiole testing. I think it runs about $25 per variety and the first test is done at bloom and later testing at veraison. Several ag schools do the testing. I think Penn State may be used by some of the Virginia vineyards.