If you grow grapes in the southern United States, you’ve likely heard of Pierce’s Disease.
If you haven’t, the fruit-production nightmare is caused by a type of bacteria known as xylella fastidiosa, it’s found in the water-conducting tissues of the plant, and it spreads from plant to plant by an insect called a sharpshooter.
Most of what you’ll read about the disease has to do with prevention — using insecticides, planting disease-resistant grapes, and so forth. That’s because once it’s taken hold, there’s little that can be done other than removing affected vines during the dormant season.
Sometimes, when phenomena like extreme weather occur, little can be done to prevent it from happening. That’s what happened at Ron Yates Wines in Central Texas, where torrential, persistent atypical rainfall throughout the early summer in 2015 created a premiere vacation destination for the glossy-winged sharpshooter, which helped itself to the new winery’s fledgling Tempranillo vines.
“Standing water had pooled everywhere,” said owner Ron Yates, who also owns nearby Spicewood Vineyards. “We also got hit hard at Spicewood that year. It took about six to seven months to manifest itself from 2016-2017.”
Some vines were eventually lost to the disease in Spicewood, which has acres of older, established foliage that were largely unaffected. In areas where the vines have experienced Pierce’s Disease, fruit production gradually slowed over a period of time before the vines were ultimately removed and replanted.
The situation at Ron Yates Wines was grim by comparison, though.
“With the younger vines, it was there,” Yates said. “It shuts down the water tissue, so the vine slowly dies. People say you can cut below it, or cut ahead of it, and you can grow it back, but it hasn’t been really a problem where (growing grapes) is really, really important.”
Yates said the disease had affected almost every vine in his Blanco County vineyard, and so he bit the bullet and made a tough decision
“I decided I would rather rip it up and start over than spend 10 years seeing which vines make it and which don’t,” he said. “We planted again in 2019 and just had a great 3½ ton harvest off about 3¼ acres here.”
The timing of the pandemic worked to Yates’ advantage with regard to his estate grapes on that property.
“We were really planning on dropping all fruit, and if it had been a normal year, we would have dropped all the fruit when the grapes were young and made some rosé (rather than stressing the vines out),” Yates said. “But everything looked good. It’s a testament to the wine in the barrel. It’s going to be spectacular.”
Signs of Pierce’s Disease on your vines include:
- Leaves becoming slightly yellow or red along margins in white and red varieties
- Fruit clusters shriveling or raisining
- Dried leaves falling, leaving the leaf stem attached to the cane
- Wood on new canes maturing irregularly, producing patches of green, surrounded by mature brown bark