Across Sonoma County, Pinot Noir vines are suffering from a
strange dieback that has long-time grapegrowers scratching their
heads.
“It’s like the top five leaves just kind of burn off. I can’t
explain it,” said Mark Houser, long-time Pinot Noir grower and
vineyard manager for Hoot Owl Creek Vineyards.
The symptoms — leaves on the shoot shriveling, dying, and
falling off — are similar to sulfur burn. But sulfur burn typically
appears when sulfur has been applied in hot weather. And of course,
the month that locals are calling “Junuary” has brought chilly
temperatures and wet weather — not heat.
“I’ve seen the same symptom when a certain chemical is sprayed
and it warms up, but it’s everywhere, not just where it’s been
sprayed,” Houser said.
Because Houser oversees different varieties with different
management practices, he’s been able to eliminate some potential
causes.
“I’ve sprayed it on Pinot and Chardonnay, and only the Pinot is
affected, so it can’t be the chemical,” Houser said.
With the wet weather, Phil Enzenauer of Enzenauer Vineyard
Management has kept busy fending off mildew in the vineyards he
manages. He first noticed the Pinot dieback in vineyards he was
tending last week.
“I told the owner, ‘Hey man, there’s something going on with the
Pinot.’ He said it’s all the same and nobody has an answer on it
yet,” Enzenauer recalled.
In fact, the syndrome is so new it doesn’t even really have a
name, and is being referred to variously as “Pinot leaf curl” or
“Pinot dieback.”
Some growers hypothesize that the symptoms are a more extreme
version of a milder leaf curl that can occur during cool weather.
But no one can recall the vines behaving quite like this.
“Pinot, about every year, you see that [leaf curl] if you have a
cold spell. But it’s probably a little more striking because of the
duration of the cold weather,” Frey said. “I think anybody that
suffered the cold weather will see some symptoms, they may vary
from vineyard to vineyard.”
The symptoms also vary from clone to clone. Clones 115, 777, and
Pommard are most susceptible, while clone 2A is more immune. Pinot
Gris, a close relative of Pinot Noir, has not been affected.
The leaf curl is widespread in Pinot Noir in Sonoma County, but
not Napa. The Carneros appellation, which straddles the county
line, has also reported symptoms.
While grapegrowers expect the fussy Pinot to bounce back and
have a successful season, the dieback may affect the growth pattern
for the year.
“When those leaves die and drop off, the bud will send out a
sucker essentially, a shoot. The plants may look a little strange,
but it should be fine,” said Nick Frey. “It could require some
different kinds of leafing or shoot removal to make sure you get
circulation through the canopy. It could mean some more hand
labor.”
While growers don’t know precisely what the dieback is, they
have a strong sense of what it isn’t. And that is good news.
Because the dieback is limited to Pinot Noir and occurred more or
less simultaneously across the county, it is unlikely to be a new
disease. And there is no evidence of insect damage from a new
invasive pest.
“There’s shoot blight, there’s stem and leaf botrytis, but this
isn’t any of that. It’s just burned the leaves off at the top …
I’ve seen migration or hatches of tomato worms or hornworms, where
they just eat the young top leaves off, but there’s no bugs,
nothing. At this point in time, I have no explanation for it,”
Houser said. “But the leaves are growing back and it’s not going to
affect the overall crop or the clusters or anything like that.”
And one of the constants across Sonoma County for the past
couple of weeks has been the unseasonably cold and wet weather.
“It’s obviously a physiological symptom, it has nothing to do
with any pathogens,” Frey said.
Lynda Hopkins can be reached at Ly***@hb*****.com.
