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Source: EuroWeekly News [edited]
A new outbreak of xylella is declared in the Valencian Community as thousands of plants have to be destroyed. The [Valencian] Department of Agriculture (DOGV) has declared [this] the 13th outbreak, affecting 9 plant species in the province of Alicante.

Experts in the region must now systematically destroy all affected plants, completely disposing of their root systems to avoid re-growth. The diseased plants are found in public and private gardens, sidewalks, medians, and other landscaped areas of the roads, highways, and motorways.

The Bacteriology Laboratory of the Ministry of Agriculture, Rural Development, Climate Emergency and Ecological Transition has confirmed that _Cistus albidus_ [rock rose], _Laurus nobilis_ [bay tree], _Lavandula angustifolia_ [English lavender], _Lavandula dentata_ [French lavender], _Polygala myrtifolia_ [milkwort], _Prunus dulcis_ [almond], _Prunus armeniaca_ [apricot], _Rhamnus alaternus_ [buckthorn], and _Rosmarinus officinalis_ [rosemary] have all been diagnosed with the disease.

[byline: Sarah Keane]
communicated by:

[_Xylella fastidiosa_ (Xf) clogs the xylem of plants, leading to wilting, necrosis, and often death. It causes many serious crop diseases such as Pierce's disease of grapevine; leaf scorch of coffee, almond, and olive (also called 'olive quick decline syndrome'); peach phony disease; plum leaf scald; citrus variegated chlorosis; lucerne dwarf; and leaf scorch of a range of other woody species. Latent infections of wild species as potential pathogen reservoirs have also been reported. Several subspecies of Xf have been proposed, and more research is needed to determine their host range and risks to crops. Initially, all strains of _Xylella_ had been classified into a single species, but a 2nd species in the genus, _X. taiwanensis_, has recently been reported as the cause of a pear leaf scorch (see ProMED-mail post 20181022.6105629).

Xf is spread by xylem-feeding insects, but also by grafting and with infected plant material. It is not seedborne. Moist conditions favour the vectors and, therefore, Xf-associated diseases. Disease management is difficult due to the large numbers of hosts and vectors, but may include use of clean planting and grafting material, as well as vector control. Both the bacterium and its main vectors are of serious international quarantine concern and are currently considered the most serious threat to European grape and fruit production. Xf has been included on the A2 quarantine list of the European Plant Protection Organisation (EPPO).

Xf had previously been reported mainly from the Americas. In Europe, its report in 2013 in olives from Italy (ProMED-mail posts 20131101.2033095, 20140820.2708739, 20140424.2425497) was thought to be its 1st report in the region. However, molecular evidence has recently shown that multiple introductions to the region must have occurred from a much earlier time (see link below). Reports from 1993 onwards of a "wood decay fungus" killing almond trees in Spain (ProMED-mail posts 20091022.3630, 20110907.2728) have now been shown to have been misdiagnosed. Xf DNA was detected in tree rings dating back to 1998, and it is thought that the pathogen then spread from the almonds to grapevines in the area (see link below). Unfortunately, a lack of diligence has resulted in failure to implement management options early on and is now leading to disastrous losses of valuable, slow-growing orchard trees in the region.

Spain autonomous communities and provinces: and

Xf leaf scorch on
- olive:, and
- almond: and
Pierce's disease of grapevine:,, and
Photo galleries of Xf vectors and symptoms on different hosts:, via and

_X. fastidiosa_ diseases, diagnosis, and vector information:,,,, (resistance), (on olive) and (on almond)
Xf strains and host range:,,, and
Xf in Europe: (evidence for multiple introductions), (pathogen ID 1993 outbreak), (impact), (summary of strains in different areas), and
Xf resources and information via:
_X. fastidiosa_ taxonomy and strains:
EPPO A2 quarantine list:
- Mod.DHA]


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