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.