A SPECIAL GROWERS’ REPORT OF AG ALERT ® CALIFORNIA Trees & Vines ®
A patch of dried-out vines, often in brown or purple hues, is a symptom of a serious vineyard threat called sudden vine collapse. The grapevine disease has been detected in nine counties in California.
A vineyard pest spreads a destructive plant disease By Bob Johnson A little more than a decade ago, grapevines scattered throughout California began suffering from a malady called sudden vine collapse. Affected plants developed stunted shoot growth early. Later, some vines began dying off, leaving nothing but the trunks and bare cordons.
At the event organized by UCCE, Eskalen asked growers and vineyard managers if they had seen sudden vine collapse. About half of the attendees raised their hands. Eskalen said researchers have documented patches of dead vines in Monterey, San Luis Obispo, Kern, Tulare, Fresno, Madera, Merced, Stanislaus and Mariposa counties. He said examinations of afflicted plants revealed they suffered from a girdling of the graft between the rootstock and scion. Eskalen said it appeared that rootstocks vulnerable to the virus were trying to separate from infected scions. The ailment generally hits vines on rootstocks, such as Freedom, that are suscep- tible to viruses. “Girdling is the rootstock killing itself rather than be infected by the viruses,” Eskalen explained. The plants also suffered from root disorders that left them unable to take water and nutrients from the soil, he said. “The vines with this disease do not have the feeder roots that take up water and nutrients, but this is not a soil-borne disease,” Eskalen said. In healthy plants, fine feeder roots peak at bloom and again after harvest.
“You see stunted shoots early in the season, followed by sudden death of the vines in the summer,” said Akif Eskalen, a University of California Cooperative Extension plant pathology specialist. The viral diseases in plants suffering collapse have been in California vineyards for years without ever causing sudden vine collapse. Then a pest caused the threat to surge. “These pathogens were in the vineyards, and it was not a big deal until we had an effective vector, the vine mealybug,” Eskalen said. “Before the vine mealybug, there was no problem.” Eskalen, who has spent the past decade studying sudden vine collapse, discussed the vineyard threat last month during the Central Coast Wine Grape Seminar in Salinas. He described tracking the plant disease, investigating causes and devising management strategies for growers.
See COLLAPSE, Page 8
April 12, 2023 Ag Alert 7
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