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Title:   Author  item
                                            Baumgartner, Kendraitem
                                            RIZZO, DAVID - UC DAVIS PLANT PATH
  Submitted to: Book Chapter
                                    Publication Type: Book / Chapter
                                    Publication Acceptance Date: 2/5/2004
                                    Publication  Date: N/A
                                    Citation: N/AInterpretive Summary: Armillaria root rot of grapevine occurs in all major grape-growing regions of the state. The causal fungus, Armillaria mellea, infects woody grapevine roots and the underlying root wood, resulting in a slow decline and eventual death of the vine. Armillaria root rot commonly affects vineyards planted on sites that were previously occupied by infected forest or orchard trees. Despite its common name of 'oak root fungus', A. mellea has a broad host range, infecting over 500 species of woody plants. Native hosts include oaks and other common forest trees such as Douglas-fir, California bay laurel, and madrone.  The fungus also infects many cultivated plants, including walnuts and other orchard trees, and many woody landscape plants. Armillaria root rot does not affect as many acres as some other fungal diseases of grapevines, but where it does occur, it is extremely difficult to eradicate and can continue to kill grapevines for many years. Vines with moderate symptoms of infection have shorter shoots and fewer clusters of fruit. Armillaria root rot tends to occur in localized sections of the vineyard, where grapevines were planted on top of buried tree roots infected by the fungus. Aboveground symptoms appear when the fungus colonizes the root collar at the base of the trunk and decays the underlying root wood. The best way to control Armillaria root rot is to avoid planting on infested sites. On infested sites, remove as many old tree roots as possible before planting. Fumigating the soil prior to planting vines often delays infection for a number of years, but it rarely eradicates the fungus completely.
                                Technical Abstract: First described on grapevines in California in the 1880s, Armillaria root rot occurs in all major grape-growing regions of the state. The causal fungus, Armillaria mellea, infects woody grapevine roots and the underlying vascular tissue, resulting in a slow decline and eventual death of the vine. Armillaria root rot commonly affects vineyards planted on sites that were previously occupied by infected forest or orchard trees. Despite its common name of 'oak root fungus', A. mellea has a broad host range, infecting over 500 species of woody plants. Native hosts include oaks and other common forest trees such as Douglas-fir, California bay laurel, and madrone.  The fungus also infects many cultivated plants, including walnuts and other orchard trees, and many woody landscape plants. Armillaria root rot does not affect as many acres as some other fungal diseases of grapevines, but where it does occur, it is extremely difficult to eradicate and can continue to kill grapevines for many years. Vines with moderate symptoms of infection have stunted shoots and a small number of clusters that ripen poorly. Armillaria root rot affects vines in localized sections of the vineyard. These disease centers tend to expand radially over time and may include a combination of dead, symptomatic, and healthy vines. Aboveground symptoms appear when A. mellea colonizes the root collar and decays the underlying root wood. The best way to control Armillaria root rot is to avoid planting on infested sites. On infested sites, the most effective control is pre-plant removal of old tree roots. Cultural controls that reduce soil moisture at the root collar may decrease the rate of colonization. Chemical controls for eradication of inoculum are limited to pre-plant soil fumigants. Soil fumigation often delays infection for a number of years, but it rarely eradicates the fungus completely.


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