Diseased!

This morning was Pinot grigio harvest day in Vinoland.  The fruit looked beautiful and the numbers came in at 27° Brix, a pH of 3.55 and TA at 6.75 - all in a good range.
The 2018 fruit may be in Vinomaker's capable hands now, but I am already thinking ahead to next year and some critical vineyard operations that will ensure a 2019 harvest.  Pruning, of course, is next up, but there is also a bit of replanting to be done.
Alas, there is evidence of Pierce's Disease (PD) in some vines (nine, one right after the other, in one row and at least one vine in the row above them).  The PD symptoms first appeared last year, but this year they are more definitely pronounced; foliar scorching, irregular bark maturity and raisining of the fruit, or, (as demonstrated in the above photograph) miniature clusters (a mere 2.4 inches).
Oh well, it'll give me something to do next spring.

The 2015 lowdown.

With the arrival of the St. Helena Cabernet Sauvignon grapes, this morning in Vinoland, the 2015 winemaking season has begun.  One small problem though: the yield is down about 50% on the previous vintage.  Most wineries, including TWWIAGE, are reporting that crops are on average about 30% down.  With the 2012, 2013 and 2014 vintages being very bountiful, some folks have been taken by surprise at the reduced size of the crop this year.  (In all honesty, this years crop size is probably closer to normal. Whatever normal is, that is.)  Vinomaker will deal with it.  The Cabernet Sauvignon grapes looked, for the most part, like their usual beautiful blue-velvet-selves.  Vital statistics were; 25.2 °B, with a pH of 3.75 and a TA of  5.85.
The 2015 growing season has not been without its problems e.g., poor fruit set and persistent drought conditions.  In addition, this particular vineyard (the source of the Clone 7), is slowly succumbing to Pierce's Disease.  I am hopeful, however, that this vintage will more than make up for what it lacks in crop with the quality of the finished wine.

Decline in the vine.

Although tourists may enjoy seeing red leaves on grapevines this time of year, red leaves are not normal and are, in fact, an indication that something is wrong with the vine. Several problems can cause red leaf symptoms in grapevines.  For example, red leaves are one symptom of Syrah Decline (SD), but they are not the only symptom.  And certainly, Syrah is not the only variety to show red leaves.
Several of Vinoland's Syrah vines display varying levels of red colouration in their dying leaves in the autumn.  (Curiously, there are fewer vines displaying redness this year than previous years.)  In the above photograph, the yellowing vine on the right is shutting down correctly - from green the leaves turn yellow, then brown, then drop to the ground - the reddening vine is shutting down not so correctly.  I needed to take a closer look, so out to the vineyard I went. A quick once over of this vine revealed, or not, as the case may be, a few things to me.
The culprit could be SD (more commonly referred to as Syrah Disorder in California), a syndrome that is said to affect particular clones of Syrah more than others.  The graft union of this particular Syrah vine shows no evidence of cracking or pitting (which are two symptoms of SD).  In fact, I'd have to say this particular vine has the prettiest of graft unions.
It can't be Leafroll disease as there is no evidence of, well, leafroll.
It isn't Fanleaf Degeneration as the leaves show no signs of deformation - as in looking like a fan.
Could it be Pierce's Disease (caused by the bacterium Xylella fastidiosa)?  Well, there is some leaf scorching, and there are a few petioles that have remained attached to the cane after the leaf blade has separated, but this vine shows no other symptoms.  No stunted shoot growth - this particular vine has shoots that are up to 8 feet in length.  No raisining of fruit - the vine supported a fantastic crop this year.
So, in conclusion, I don't know what is wrong with this vine.  If I really wanted to know what was going on I could have the tissue tested.  Then again, I could not.  Perhaps it is a hitherto unknown pest...that'd just be my luck. Ho hum.