Xylella fastidiosa
Xylem-inhabiting fastidious bacteria Introduction The bacteria multiplies in the vessels and these become blocked, and water can not reach all parts of the plant from the roots and infected plants essentially begin to suffer from drought Transmitted by xylem-feeding insects. The pathogen is maintained in the gut of the vector and adults need to feed on infected plants in order to acquire and transmit the pathogen. Cercopoidea (spittlebugs or froghoppers) Cicadoidea (cicadas) Membracoidea (which includes single xylem fluid-feeding subfamily, the Cicadellinae, known as sharpshooters)
Xylella fastidiosa cells
Vectors
Introduction The meadow spittlebug (Philaenus spumarius) is the main vector identified in Europe to date and is the primary vector in Italy This species is widespread in Europe (including the UK) and feeds on hundreds of hosts
Introduction The bacterium overwinters in the xylem of the host plant as well as in weeds. The bacterium is not seed-borne and is not mechanically transmitted Mainly in tropical and subtropical areas (optimum growth temperature: 26-28 C) Most subspecies of Xylella are killed by freezing temperatures There are reports of Xylella in regions of the USA/Canada with similar winter temperatures to the UK Bacterial Leaf scorch diseases occur in much colder climates Host range comprises plants in 69 families, 187 genera and more than 300 plant species. Numerous wild plants and weeds can carry the bacterium without symptoms (e.g. wild grasses, sedges, lilies, various bushes and trees)
The causal agent of Pierce s disease of grapevine, phony peach disease, plum leaf scald, almond, elm, oak, American sycamore, mulberry and maple leaf scorch, and citrus variegated chlorosis disease, among other diseases 18/10/2018
Subspecies Xylella fastidiosa - four characterised subspecies Xylella fastidiosa subsp. fastidiosa Pierce Disease on grapevine and almond leaf scorch Xylella fastidiosa subsp. pauca South American strains causing citrus variegated chlorosis and coffee leaf scorch Xylella fastidiosa subsp. sandyi Oleander in California and Texas Xylella fastidiosa subsp. multiplex Endemic to North America, numerous host but generally not grapevine and it is most frequently associated with trees (particularly urban trees) 18/10/2018
Xylella fastidiosa distribution Xylella fastidiosa Source: EPPO (purple transient, yellow present)
Xylella fastidiosa distribution Germany 2016 subsp. fastidiosa on four plants of different species in nursery Xylella fastidiosa Mainland Spain 2017 subsp. multiplex in almond plantation Corsica 2015 & southern mainland France 2016 - subsp. multiplex, mostly on ornamentals eg. Polygala myrtifolia (milkwort). One incidence of subsp. pauca Balearics 2016 & 2017 subsp. fastidiosa, multiplex & pauca. Initially on cherry in Mallorca, now widening range of host species. Italy (Apulia region) 2013 - subsp. pauca on olive, almond & oleander
Italy Surprisingly, olive (Olea europaea) has rarely been mentioned as a host plant in the literature However, studies were recently initiated in Southern California because increasing olive tree mortality was reported from Los Angeles area. X. fastidiosa was consistently detected in olive trees showing branch dieback and leaf scorching but its pathogenicity could not be fully demonstrated (Krugner et al., 2010)
Italy Olive Quick Decline Syndrome (OQDS): Withering and desiccation of scattered terminal shoots Rapidly spread to the rest of the canopy Collapse and death of the tree
Italy
Italy
On Polygala Myrtle-leaf milkwort (Polygala myrtifolia)
On Oleander Oleander (Nerium oleander)
Xylella fastidiosa on urban trees Bacterial Leaf Scorch
The disease BLS (Bacterial Leaf Scorch) is recognised as a major disease of street and landscape trees in the mid-atlantic and southeastern United States since 2010 Symptoms on trees are not always distinct: e.g. on Quercus palustris the disease appears as early senescence with no distinct pattern of necrosis The first report of Xylella on trees was on American elm (Ulmus americana) in 1959 (Wester & Jylkka) Since the 1980s: Reported on red oak (Quercus rubra). Other oak species affected: Q. coccinea, Q. falcata, Q. imbricaria, Q. laurifolia, Q. palustris, Q. shumardii, Q. virginiana Reported on sycamore (Platanus occidentalis) Reported on maple (Acer rubrum) Xylella on trees
On elm (Ulmus sp.) (Brian Olsom, Oklahoma State University, Bugwood.org)
On elm (Ulmus sp.) (Brian Olsom, Oklahoma State University, Bugwood.org)
On elm (Ulmus sp.) (Sandra Jensen, Cornell University, Bugwood.org)
On wych elm (Ulmus glabra) (Elizabeth Bush, Virginia Polytechnic Institute and State University, Bugwood.org)
On Quercus spp. Quercus robur Quercus coccinea Quercus palustris Quercus imbricaria John Hartman John Hartman, University of Kentucky, Bugwood.org
On Quercus rubra (John Hartman John Hartman, University of Kentucky, Bugwood.org)
On Quercus palustris (John Hartman John Hartman, University of Kentucky, Bugwood.org)
On Platanus occidentalis (Edward L. Barnard, Florida Department of Agriculture and Consumer Services, Bugwood.org)
On Platanus occidentalis (Theodor D. Leininger Theodor D. Leininger, USDA Forest Service, Bugwood.org)
On Acer negundo (John Hartman John Hartman, University of Kentucky, Bugwood.org)
On Acer sp. (John Hartman John Hartman, University of Kentucky, Bugwood.org)
On maple (Acer spp.) (Sandra Jensen, Cornell University, Bugwood.org)
On Liquidambar styraciflua (John Hartman John Hartman, University of Kentucky, Bugwood.org)
On common hackberry (Celtis occidentalis) (John Hartman John Hartman, University of Kentucky, Bugwood.org)
On Ginkgo biloba (Elizabeth Bush, Virginia Polytechnic Institute and State University, Bugwood.org)
Symptoms Can affect trees over many years Symptoms might appear in one branch or part of the crown Leaves develop various patterns of marginal or interveinal necrosis (with or without a chlorotic halo) Leaf symptoms develop in midsummer and progress in severity towards the autumn Reduction of growth and seed set, flower abortion Long-affected trees eventually develop dieback (although other factors might be also responsible for this symptom) Infected trees are usually removed because of their appearance or potential hazard, not because of tree death Elms may be killed outright by the disease Other affected trees eventually decline to the point where dead branches pose a risk or they are unsightly Decline may occur quick or slow depending on the tree species and the environment Secondary pests and diseases may be present and responsible for some of the symptoms
Many plant species are reported as hosts of X. fastidiosa without expressing symptoms. In addition, in many host plants the development of symptoms can occur months or years after infection. This makes early detection and surveys of X. fastidiosa difficult
Information available https://gd.eppo.int/taxon/xylefa https://www.eppo.int/quarantine/special_topics/xylella_fastidiosa/xylella_fastidiosa.htm Information on our website (http://www.forestry.gov.uk/forestry/beeh-a3vemx) Pest Alert: https://www.forestry.gov.uk/pdf/fcph-xf.pdf/$file/fcph-xf.pdf https://planthealthportal.defra.gov.uk/assets/factsheets/xylellafastidiosa2015.pdf https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/598470/xylella-fastidiosa-impl-trade.pdf https://www.ponteproject.eu/
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