| Pierce's disease |
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| Xylella fastidiosa |
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Plant hosts
- Major hosts: Acer (maples), Acer saccharum (sugar maple), Citrus latifolia (Tahiti lime), Citrus reticulata (Mandarin orange), Citrus reticulata x paradisi (tangelo), Citrus sinensis (navel orange), Liquidambar styraciflua (sweet gum), Medicago sativa (lucerne), Morus alba (mora), Nerium oleander (oleander), Platanus occidentalis (sycamore), Prunus angustifolia (mountain cherry tree), Prunus dulcis (almond), Prunus persica (peach), Prunus salicina (Japanese plum), Pyrus (pears), Ulmus (elms), Vitis labrusca (fox grape), Vitis rupestris (sand-grape), Vitis vinifera (grapevine)
- Wild hosts: Brachiaria (signalgrass), Coffea (coffee), Conium maculatum (poison hemlock), Cynodon (quickgrass), Cyperus (flatsedge), Digitaria (crabgrass), Echinochloa frumentacea (Japanese millet), Fragaria vesca (wild strawberry), Lolium (ryegrass), Lolium multiflorum (Italian ryegrass), Medicago (medic), Paspalum, Paspalum dilatatum (dallis grass), Passiflora foetida (red fruit passion flower), Poaceae (grasses), Rubus (blackberry, raspberry), Sambucus (elderberry), Taraxacum officinale (dandelion), Trifolium (clovers), Vinca minor (common periwinkle)
To view larger image click on picture.
Image provided by Rebecca A. Melanson, Louisiana State University AgCenter, U.S.
Means of movement and dispersal
Plant parts liable to carry the pest in trade and transport:
- Bulbs, tubers, corms and rhizomes: spores are born internally and are visible under light microscope.
- Fruits: spores are born internally and visible under light microscope.
- Flowers: spores are born internally and visible under light microscope.
- Leaves: spores are born internally and visible under light microscope.
- Seedlings and micropropagated plants: spores are born internally and visible under light microscope.
- Roots: spores are born internally and visible under light microscope.
- Stems: spores are born internally and visible under light microscope..
- Seeds: spores are born internally and visible under light microscope.
Plant parts not known to carry the pest in trade and transport:
- Growing medium accompanying plants.
- Wood.
- Bark.
Symptoms
Symptoms appear when a significant amount of xylem becomes blocked by the bacteria's growth. Any other problem that blocks, inhibits or limits water from getting to the leaves will produce similar symptoms. Dryland grapes grown in western Oregon during the drought of 2001 displayed some of these symptoms. Fungal cankers, damaged trunks, girdeling roots, gopher damage, and root rots also can produce similar symptoms.
Symptoms of Pierce's Disease first appear as water stress in midsummer. Leaves become slightly yellow or red along margins in white and red varieties, respectively, and eventually leaf margins dry or die in concentric zones. Fruit clusters shrivel or raisin. Dried leaves fall, leaving the petiole attached to the cane. Wood on new canes matures irregularly, producing patches of green, surrounded by mature brown bark. 'Pinot Noir' and 'Cabernet Sauvignon' have high regular zones of progressive marginal discoloration and drying on blades.
Usually only one or two canes will show Pierce's Disease symptoms late in the first season of infection. Symptoms gradually spread along the cane from the pont of infection out toward the end and more slowly toward the base. Cane tips and roots may die back. Vines deteriorate rapidly after symptoms appear. Shoot growth in infected plants becomes progressively weaker as symptoms become more pronounced.
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