Collapse Continued from Page 7
Soil-borne pathogens such as fusar- ium and macrophomina charcoal rot can cause young vine decline, which prevents new plants from ever becoming vigorous and productive. Mature vines suffering vine collapse did not have the diseases, Eskalen said. Researchers examined 405 vines suf- fering the malady. Some 96% tested pos- itive for grape leafroll virus. The vines generally also had other viruses. Once the vines have collapsed, Eskalen said, they will not recover, as damage from a cocktail of viruses just gets worse each year. A decade ago, a Southern California grower brought grape wood back from a trip to Israel. Researchers say the first vine mealybugs hitched a ride to California and steadily spread throughout the state. The vine mealybug is a particularly ef- fective insect vector. It hides from inspec- tion or insecticide applications, and it pro- duces three to seven generations a year. Often the most visible sign of a vine mealybug infestation is the honeydew that attracts ants, which can protect the vine mealybugs from predators. In 2020, Eskalen and fellow UCCE vi- ticulture farm advisors across the state produced a guide with management suggestions for sudden vine collapse.
Akif Eskalen, right, a University of California Cooperative Extension specialist in plant pathology, advises growers on managing sudden vine collapse. The disease is spread by the vine mealybug.
Their report, “Sudden Vine Collapse: Current Understanding of a Disease Complex,” may be found at ucanr.edu/ sites/eskalenlab/files/320825.pdf. In outlining the extent of sudden vine collapse in some areas of California, the
report noted, “In some cases, patches are so large that they can be seen via satellite images on Google Earth, with levels of loss that have caused growers to remove entire vineyards.” The report said Freedom rootstock, in particular, looks to be the most suscep- tible to sudden vine collapse. It recom- mended that, “in the case of replanting, farmers may want to start thinking about changing to less sensitive rootstocks.” The document also noted that the first step in a management program is to test suspect vines to confirm they have the complex of viruses that cause sudden vine collapse. If they test positive, the next step is to act decisively to make sure the infections are contained and do not spread to healthy areas of the vineyard. “Management for this emerging dis- ease should include tests to confirm co-infection of the viruses, removal of
infected grapevines and vector control,” Eskalen and fellow farm advisors wrote in the report. Containment may be difficult, howev- er, because nothing kills the viruses once they are in grapevines While growers can slow the spread and population increase of the vine mealybug, no one has found a way to eliminate this pest once it is established in a vineyard, Eskalen said. The answer may be to remove and re- place entire sections of the vineyard and to take care to minimize the danger of reinfection, researchers say. Unfortunately, Eskalen said, the only answer for some infected vineyards may be to write off the crop loss and just walk away from the problem. (Bob Johnson is a reporter in Monterey County. He may be contacted at bjohn11135@gmail.com.)
2023 Health & Safety on the Farm and Ranch
California Farm Bureau is pleased to offer this year-long program of training sessions presented by Nationwide. Select topics will be presented in both English and Spanish. Members, enjoy access to free classes! Register for the upcoming training webinars. Trainings will be presented via Zoom. The Hazardous Agricultural Materials (HAM) training must be attended in person at a participating County Farm Bureau office or at the California Farm Bureau office in Sacramento. For a list of class dates and to register, visit cfbf.com/FBE or call (800) 698-FARM for assistance. You will receive a Zoom link and details two days prior to your selected webinar date.
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8 Ag Alert April 12, 2023
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