Home   /   Resources   /   Xylella

Xylella

The Biosecurity Plan for the Olive Industry (Version 2.0 October 2016) identifies the following high priority exotic pests and diseases of olives in Australia – are you able to recognise these?

THERE ARE TWO XYLELLA SUBSPECIES THAT AFFECT OLIVES:

 

Xylella fastidiosa is a bacterial pathogen that infects over 360 different plant species, including olives. There are several strains (subspecies) of this bacterium; some are limited to certain plant hosts.

At least two strains affect olives and are considered a biosecurity risk as they have not been detected in Australia. They are: X. fastidiosa subsp. pauca and X. fastidiosa subsp. multiplex.

The bacteria live in the plant xylem (water-conducting) vessels, inhibiting the uptake of water and nutrients which leads to disease symptoms that look like water stress – called leaf scorch.

A particular strain of X. fastidiosa subsp. pauca–called Olive Quick Decline Syndrome (OQDS) –causes dieback, and death of trees. OQDS was first reported in olives in southern Italy in 2013, but has since been reported more widely, including in Brazil.

Most introductions of X. fastidiosa occur with the movement of infected plant material. Once present, xylem-feeding insect vectors including leafhoppers and spittlebugs are the primary pathway by which it is spread through a country or region.

Hence, known exotic vectors of Xylella are included in the listed biosecurity threat. There is currently no known cure or treatment for X. fastidiosa infections.

Once plants are infected with Xylella, eradication is extremely difficult; therefore prevention is the most effective approach.

Some olive varieties e.g. Leccino and Favolosa FS-17 appear to be more tolerant while Kalamata, Coratina and Cellina are the worst affected.

Leaf Scorch: Xylella fastidiosa subspecies multiplex (with vectors):

The subspecies X. fastidiosa subsp. multiplex is considered to be a new genetic variant of the bacterium, different to that found in Italy.

OLIVE QUICK DECLINE SYNDROME (OQDS): XYLELLA FASTIDIOSA SUBSPECIES PAUCA (WITH VECTORS)

Symptoms include leaf scorch and desiccation of twigs and branches, beginning at the upper part of the crown and then moving to the rest of the tree, which acquires a burned look.  There is no known practical treatment once a plant has been infected and it will eventually die.

The bacterium is transmitted between plants via insect vectors which feed on plant sap (such as the meadow froghopper). Spread of the disease over longer distances occurs when Xylella-infected plants are moved in trade.

Xlyella is currently spreading from the Puglia region of Italy to other Mediterranean olive production regions. The disease has also been detected in olive crops in California, Argentina and Brazil.

Xylella is also known to naturally infect many commercial, ornamental and native plants from more than 300 species, with this number ever increasing.

As it is transmitted by xylem feeding insects, we need to know which insect species in Australia are the potential vectors to effectively target.

ON-FARM BIOSECURITY PLANNING

All olive producers are strongly encouraged to implement an on-farm biosecurity plan using the Farm Biosecurity Action Planner For Olive Growers – right click to open link

Also post biosecurity signage at your property entrances – signs may be purchased from the AOA shop.

Further information on Biosecurity Best Practice is available on the AOA website here.

IF YOU SUSPECT A NEW PEST, CALL THE EXOTIC PLANT PEST HOTLINE:

Xylella Resources:

2019 AOA Conference Presentation

Xylella – Act Like It Is Already Here

By Craig Elliott, National Xylella Co-ordinator, Manager National Xylella Preparedness Program

Presentation slides

Video

Nowhere has the economic and social impacts of Xylella been more dramatically demonstrated than the olive groves of Italy. With over 560 species of plant hosts and present in multiple regions around the world, Xylella is prioritised as Australia’s number 1 plant biosecurity threat. This presentation covers the key activities of the National Xylella Preparedness Program and key steps growers need to take to protect their properties and businesses from Xylella and other biosecurity threats.

Is Xylella a threat to Australian olives?

December 2019 R&D Insights pp 4-5

Xylella fastidiosa articles in the Olive Oil Times

END

Updated: 7/4/2021