Olive tree dying

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Olive grove in Surano (LE) infested with Xylella fastidiosa (2019). It can be seen that the infected trees are losing their leaves and the owners try to contain the spread of the bacterium by sawing off the branches.

The olive tree mortality was first observed in Europe in southern Italy. The cause of the olive quick decline syndrome (OQDS) is the bacterium Xylella fastidiosa . In 2013, the olive tree dying in Puglia became known and has since spread northwards. Branches of the olive oil production are affected by large-scale failures.

Homalodisca vitripennis , a dwarf leafhopper , can transfer the bacterium into the xylem of the plant when it sucks in the sap.

Origin, Symptoms and Distribution

The OQDS, olive quick decline syndrome , affects olive trees in a special way due to rapid death. Monocultures with olive trees and cicadas favor the spread of olive tree death in southern Italy. The cicada Homalodisca vitripennis , which can transmit the bacterium when sucking plant juices, is considered to be the carrier of the pathogen . The origin and route of the bacterium to Europe is unclear, and no remedies are known in the 2010s.

Infested olive trees can be recognized by the clear wilting of the crown. The leaves occasionally turn yellow, sometimes brown, curl up and finally dry up. Often the leaves stick to the branches.

In 2013, 8,000 hectares (ha) in southern Italy were affected; in 2015, hundreds of thousands of olive trees could no longer be saved on around 230,000 hectares.

The disease (also known as Pierce's disease ) causes trees to die by drying out. The trigger is the bacterium Xylella fastidiosa (dt. Fire bacteria ), which clogs the pores of the plant vessels ( xylem ) and thus blocks the transport of water and nutrients. Infested olive trees ultimately die from lack of water.

Control and Prevention

The vector is mainly combated ; Infested trees are felled early. Many olive tree owners also try to curb the spread of bacteria by cutting off visibly infested branches (see picture). Since November 2015, attempts have been made at the University of Foggia to increase the tree's own production of phytoalexins , which are naturally produced again after the penetration of microorganisms for defense in the affected tissue. By 2019, Puglia was divided into regions in order to counteract olive tree death: a "buffer zone" at Taranto , a "containment zone" between Taranto and Brindisi and an "infested zone" which includes Brindisi, Lecce and their regions.

criticism

European institutions criticized the handling of the Italian authorities with the olive tree death because of "serious neglect".

literature

  • SM. Mang, S. Frisullo, HS. Elshafie, I. Camele: Diversity Evaluation of Xylella fastidiosa from Infected Olive Trees in Apulia (Southern Italy) . April 2016. In: J Microbiol Methods. PMID 27147930
  • Giovanni Paolo Martelli: Il disseccamento rapido dell'olivo: stato delle conoscenze (olive quick decline syndrome, OQDS), Dipartimento di Scienze del Suolo, della Pianta e degli Alimenti, Università degli Studi Aldo Moro - Bari, 2015, ( online PDF )
  • Rodrigo Krugner, Mark S. Sisterson, Jianchi Chen, Drake C. Stenger: Evaluation of Olive as a Host of Xylella fastidiosaand Associated Sharpshooter Vectors , 2014, (online PDF)

Web links

Individual evidence

  1. ↑ a b BIOSECURITY SA: Factsheet: OLIVE QUICK DECLINE SYNDROME ( Memento of April 9, 2018 in the Internet Archive )
  2. ↑ a b c Spektrum.de, July 5, 2017, Alison Abbott: Mass death in the olive grove ( Memento from July 5, 2017 in the Internet Archive )
  3. ↑ a b Spiegel online: Tree dieback: Fire bacteria destroys olive groves in southern Italy ( Memento from December 8, 2013 in the Internet Archive )
  4. ↑ Badische-zeitung.de, March 26, 2015, Julian Müller-Meiningen: Fire bacteria kills olive trees in southern Italy ( Memento from April 2, 2015 in the Internet Archive )
  5. ↑ Ylenia Granitto: Strategy to Contain Xylella Fastidiosa Organically Shows Promise , in: Olive Oil Times, August 25, 2016.
  6. ↑ merum.info: Xylella - Olive tree die-off ( Memento from July 11, 2019 in the Internet Archive )