The MGS Forum
Gardening in mediterranean climates => Pests and diseases => Topic started by: JTh on January 13, 2015, 11:25:09 AM
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I heard about this new threat for the first time on the radio this morning, and I thought this was rather scaring and I wonder if any of you have had any experience with this disease, which has now infected olive tree in a large part of Puglia, southern Italy. This area is responsible for more than a third of Italy’s total olive production
The bacterium, Xylella fastidiosa, has probably been imported from the American continent, where is has been known to cause phoney peach disease in the southern United States, bacterial leaf scorch, oleander leaf scorch, and Pierce's disease, and citrus variegated chlorosis disease in Brazil (ref. Wikipedia), and now also olive trees in Italy, where it was recently introduced (http://www.eppo.int/QUARANTINE/special_topics/Xylella_fastidiosa/Xylella_fastidiosa.htm).
The bacterium is spread by sap-feeding insects (spittlebugs and leafhoppers), it colonizes and blocks the tree's water conducting tissues or xylem and the water transport becomes disrupted in roots, branches, and leaves due to large amounts of multiplying bacteria. The bacteria also produce a gel, which clogs the transport system even more. The result is initially leaf scorching, and then slowly the death of the tree.
There is no cure, and control methods seem to be few, if any at all. I wonder if any of you have met this problem in Europe, I suppose it is important to discover it as soon as possible and try to prevent it from spreading further, if possible, it sounds rather frightening to me.
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Andrew Sloan in a post about olive crop production reported that olive production is down in Italy because of a disease associated with oleanders. I wondered what the connection could have been. It sounds very much like this Xylella fastidiosa which you describe JTh.
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It could be the same infection. It is taken very seriously by EFSA, and they have introduced buffer zones around affected areas in southern Italy. There was an article about this in The Guardian last week (http://www.eppo.int/QUARANTINE/special_topics/Xylella_fastidiosa/Xylella_fastidiosa.htm).
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The bacterium infects an enormous range of plants, so once it gets a hold anywhere almost any plant - not just woody ones, either - can serve as a reserve of infection, as it's passed from plant to plant by sap-sucking insects. Besides the crops mentioned by Jorun, it causes serious losses in US vineyards, and can be very damaging to other stone fruits including almonds, as well as olives.
A lot depends on the ability of the Italians to control their buffer zones!
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More info:
- mentioned in the RHS's 'The Garden', feb16 (edging closer to the UK; found in mainland France)
- http://www.forestry.gov.uk/forestry/beeh-a3vemx
- http://nature.berkeley.edu/xylella/
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See Brian Chatterton's article on the website www.mediterraneangardensociety.org/olives.html (http://www.mediterraneangardensociety.org/olives.html) for October 2015.