Xylella fastidiosa

Olive tree infected by Xylella fastidiosa, dry leavesThe Xylella fastidiosa is a bacterium recently introduced in Europe. It is especially virulent in olive tree, it affects numerous plants, trees and fruit trees.

For now is not known cure or effective treatment against the disease.

Most of the existing olive varieties are sensitive to this bacterium.

Curiosities: looking for the alarm and sensationalism the disease has been published in multiple media press as Ebola del olivo . However, researchers are not convinced by the name, because Ebola is a virus and Xylella fastidiosa is a bacterium. Despite this discrepancy, the difficulty of combating or curing the Xylella fastidiosa is of similar or greater magnitude than the case of Ebola.

The annoying surname is received due to the difficulty that researchers have to cultivate bacteria in the laboratory.

Subspecies of Xylella fastidiosa

Subsp. annoying: especially affects vid, almond and Alfalfa. This is the species currently present in Spain (Islas Baleares and Alicante).

Subsp. multiplex: in addition to the olive tree, it affects fruit trees of the genus Prunus spp. (plum tree, cherry tree , peach tree, apricot tree, almond tree… ), Quercus spp. (oak, holm oak, cork oak…), Ulmus spp. (elm trees), Rubus spp. (blackberries) and Morus spp. (mulberry) Strains of this subspecies of Xylella fastidiosa have appeared in Spain, France and Italy (Apulia).

Subsp. pauca: It affects the olive tree, orange tree, coffee tree…

Olive Ebola Cycle

The bacteria enters the xylem of the plant through transmission by sap sucking insects. In the Mediterranean olive grove the cicada or cicada (Homalodisca vitripennis) is the main transmitting vector of the disease.

The insect, after feeding on an infected tree, carries the bacteria and infects healthy trees when it feeds on them.

Xylella fastidiosa bacterium under a microscope The bacterium develops quickly with temperatures of 25-28ºC. However, it is sensitive to temperatures below 15 ° C. Extreme temperatures that exceed 34ºC or lower than 10ºC limit the survival of the bacteria.

When multiplied, the bacteria block the flow of sap from the plant, drying the branches and leaves of the olive tree.

Therefore, Xylella fastidiosa prefers areas of mild winters, where it has a more aggressive behavior.

More than 300 species of plants, fruit trees and trees are susceptible to infection.

All xylem sucking insects are possible carriers and transmitters of the disease.
Note: Because of its virulence, at present, it is one of the diseases of the olive tree most feared.

Diseases induced by the bacteria

In the vineyards produces the Pierce’s disease, the leaves are dried from the outside to the inside, appearing chlorotic and necrotic spots.

Citrus suffer variegated chlorosis.

In alfalfa and peach, dwarfism occurs.

Finally, Xylella fastidiosa affects the olive, almond, cherry, oleander, oak, banana tree, elm, blueberry…. It affects these species by singeing partially the leaves or by drying them completely.

Xylella fastidiosa in Italy

The first detection occurs in the province of Lecce, in southern Italy, in the region of Apulia. In October of the year 2013.

map of Apulia and province of Lecce In April of 2014 the phytosanitary emergency status is declared:

eradicate trees with symptoms of the disease.

Demarcate the affected areas by establishing buffer zone and phytosanitary cord.

They control the transmitting vectors of the disease.

Prohibit the transport of infected plants.

In March of 2015 the area of infection approaches 300,000 hectares (1% of the total area of Italy).

Affected trees that have been destroyed exceed million olive trees based on the disclosed data.

Xylella fastidiosa in France

The first positive is detected in July of 2015 in southwest Corsica. By October 2016, almost 300 outbreaks had been detected. Only the central area of the island is practically free.

Areas affected by Xylella fastidiosa in Spain

In October of 2016 the positive first is detected in a greenhouse in Porto Cristo (Mallorca).

However, it is believed that the bacterium has been on the island for at least 10 years and is the cause of the death of more than 12,000 hectares of almond trees.

In Mallorca as well as in almond, positive have been given in vid and olive.

In June of 2017 the positive first is detected on the peninsula (Alicante), the affected tree is a almond tree.

Treatment against Xylella fastidiosa

Unfortunately there is no effective remedy or cure to combat Xylella fastidiosa. Treatments with antibiotics could control the bacteria. However, these are not authorized in Europe because of their dangerous repercussions.

The techniques of control of expansion of the bacteria focuses on combating the insect transmitters of the disease. The implementation of applications with insecticide products are the treatments that are currently being used

Resistant olive varieties

In Italy research is being carried out in search of bacterial tolerant varieties. The results of these studies show Leccino as a resistant variety and Cellina de Nardò as very sensitive.

Recommended Reading

In addition to the Xylella fastidiosa there are other bacteria, fungi and insects that affect the olive tree : Tuberculosis of the olive tree , Verticillium , Fly of the olive tree , Prays , Cochineal , Repilo , Glifodes , Acariosis of the olive tree , Nematodos

Warning

A significant part of the information, comes from Spanish research organizations. When phytosanitary products are used, it is important to verify that their use is currently authorized in the country of application.

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