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Xylella fastidiosaA biosecurity threat to Australia

Xylella causes significant environmental and economic impacts, and many commercial and ornamental plant species are susceptible. Every year tests show more plant species are capable of being infected, and it is spreading around the world. Although it is not present in Australia it is of major concern to our plant industries and environment.

Why we are concerned about Xylella

Overview of Xylella

• Xylella is known by a number of common names, depending on the host, including:

• Pierce’s disease, California vine disease, Anaheim disease (in grapevine)

• dwarf (in lucerne), phony disease (in peach)

• leaf scald (in plum)

• bacterial leaf scorch (almond, coffee, elm, maple, mulberry, oak, oleander, sycamore)

• variegated chlorosis (in citrus)

• wilt (in periwinkle)

• Only one species, but several subspecies which affect different hosts

• Accepted names: fastidiosa, multiplex, sandyi, pauca

• Proposed names: morus, tashke

3Xylella fastidiosa - A biosecurity threat to Australia

Symptoms

• Xylella may not cause symptoms in all host species and these symptoms can vary between hosts

• Transmission from asymptomatic to symptomatic hosts is common

• Infection clogs the infected plant’s fluid vessels, blocking movement of water, and killing even a mature tree in 1-2 years

• Symptoms are easily confused with water stress or the presence of other pathogens, and can include:

• leaf discoloration/scorching

• browning and loss of leaves

• stunting of young shoots

• gradual reduction in fruit size over time

• dieback and eventual death of the plant.

4Xylella fastidiosa - A biosecurity threat to AustraliaSource: E. Barnard, invasive.org

Transmission and infection

• Xylella is a bacterium that is found only in the fluid vessels (or xylem) of plants

• It is transmitted by:

• Moving live planting material

• Sap sucking insects such as sharpshooters, leafhoppers, aphids and spittlebugs

• It is NOT transmitted by seeds or mechanically (such as pruning equipment)

• Greatest impacts are in areas with mild winters


Well known effective vectors

Glassy winged sharpshooter, Homalodisca vitripennis

Source: C. Ray, invasive.org

Blue-green sharpshooter, Graphocephala atropunctata

Source: C. Moorehead, invasive.org

Dilobopterus costalimai

Source: A. Cymru, National Museum WalesMeadow froghopper, Philaneus spumarius

Source: Wikimedia commons

Scientific name Common name(s) Associated host disease

Acrogonia terminalis Citrus variegated chlorosis

Cicadella viridis Green leafhopper Pierce’s disease

Dilobopterus costalimai Citrus variegated chlorosis

Draeculacephala minerva Green sharpshooter Pierce's disease

Graphocephala atropunctata Blue-green sharpshooter Pierce's disease

Homalodisca vitripennis Glassy winged sharpshooter Pierce's disease

Oncometopia fasciali Citrus variegated chlorosis

Philaenus spumarius Spittlebug, meadow froghopper Olive quick decline

Xyphon fulgidum Redheaded sharpshooter Pierce's disease


* note that none of the vectors in this table are known to occur in Australia

Global distribution

• Europe: France (including Corsica, under eradication), Italy (under eradication), Germany (under eradication)

• Asia: Iran (restricted), Taiwan (endemic)• North America: Canada, Mexico, USA (endemic, widespread)• Central America: Costa Rica, Puerto Rico• South America: Argentina (endemic), Brazil (endemic), Paraguay (endemic),

Ecuador, Venezuela http://www.cabi.org/isc/datasheet/57195


Host range

• Extremely wide host range

• could affect a large number of crops, ornamental, and environmental trees

• constantly expanding as it is discovered on new hosts

• More than 368 plant species (including nine hybrids) are confirmed hosts, in 279 genera and 91 families

• Differences in host range exist amongst subspecies and within particular subgroups/genotypes within a subspecies

• High amount of genetic variability between the subspecies, and new strains may emerge


Subspecies


Subspecies name Host(s) Associated disease(s) Found in

Subsp. fastidiosaAlfalfa, almond, grape, maple

Almond leaf scorch,Pierce’s disease of grapevines

North America, Central America, Iran, Taiwan

Subsp. multiplex

Almond, blueberry, elm, peach, pigeon grape, plum, sycamore

Phony disease of peach, plum leaf scald

North and South America, France

Subsp. pauca Citrus, coffee, olive Citrus variegated chlorosis South America, Italy

Subsp. sandyi Oleander Oleander leaf scorch North AmericaSubsp. morus(proposed) Mulberry Mulberry leaf scorch North AmericaSubsp. tashke(proposed)

Chitalpa(ornamental hybrid) North America

Pear leaf scorch Pear Pear leaf scorch Taiwan

Symptoms of plum leaf scaldSource: University of Florida

Symptoms of citrus variegated chlorosisSource: A. Purcell, invasive.org

Symptoms of Pierce’s disease on grapevineSource: A. Purcell

Xylella has historically existed on grapevines in the Americas, but has in more recent times rapidly expanded host range, crops impacted, and also distribution, including into Europe for the first time.

Global situation

Timeline of events


Jul 2016: First detection of Xylella in Germany on oleander

Nov 2015 : Australia implements emergency quarantine measures for Xylella

Mid 2015: Xylella identified from ornamental plants in France

Feb 2014: Emergency measures adopted by the European Union

Oct 2013: Olive quick decline syndrome in Italy attributed to Xylella

2000: Complete genome sequence of Xylella published in Nature

1996: Glassy winged sharpshooter is discovered in California, threatening wine regions

1995: Xylella found to cause coffee leaf scorch in Brazil

1987: Citrus variegated chlorosis observed in Brazil. Later observed in Argentina

1974: Almond leaf scorch described

1880s: Pierce’s disease devastates vineyards of Southern California

Impacts

• High number of unknowns

• Economic impacts

• Pierce’s disease is costing California $104 million per year

• 3 major citrus regions had 44-63% of commercial trees with fruit symptoms

devastated in 2005 in Brazil and Argentina

• Plum leaf scorch caused the loss of entire orchards in Brazil and Paraguay within

several years after the disease first appeared

• More than 1 million ancient olive trees have died in Italy

• The cost of olive oil has increased by 20% across the EU

• Social Impacts

• Loss of livelihoods for farmers, and regional identity

• Death of ornamental and amenity trees susceptible to the bacterium


Xylella fastidiosa - A biosecurity threat to Australia 13

Olive decline in Italy

• Initially unclear cause of a new disease of olives in southern Italy, called

Olive Quick Decline Syndrome

• Thought to be introduced ~2008-2010

• Oct 2013, pathogen identified as Xylella fastidiosa subsp. pauca

• Century old olive trees which have become a key part of the landscape,

economy, and identity of the region have been wiped out

• Demarcated zones around affected areas in the Province of Lecce, in

Apulia region

• Including buffer zone where all host plants are to be destroyed

An incursion of Xylella into Australia would place entire industries, our unique native flora, along with important social or heritage trees at risk. Because of this risk, emergency measures have been put in place and a range of preparedness activities initiated. There is no evidence of Xylella being successfully eradicated once it has established with an effective vector.

What this means for Australia

Current status in Australia

• Australia is absent of Xylella

• Absent: no pest records (ISPM 8 – Determination of pest status in an

area)

• Phytosanitary measures in place to prevent entry

• Xylella and Homalodisca vitripennis (vector - glassy winged

sharpshooter), and other exotic vectors are notifiable pests

• Reporting systems in place to report any detections

• No other records indicating the presence of Xylella

• Australia conducts ongoing surveillance


Regardless, we can’t afford to be complacent

Emergency measures

• Strengthened existing measures over time

• Nursery stock and plant material coming from risk areas require testing

and freedom certification

• Approved arrangement requirements for off-shore testing and

certification of nursery stock from high risk countries

• Material not meeting requirements may be held and tested in an approved

facility for 12 months or nursery stock material may be hot water treated,

followed by standard screening arrangements

• Taken a broad approach to hosts

• Regulation of 89 plant families since November 2015

• High risk countries - all countries in the Americas and Europe, as well

as India, Iran, Lebanon, Taiwan and Turkey

• Low risk countries - includes all countries not identified as high risk

• Import conditions are available on BICON at: bicon.agriculture.gov.au


Preparedness

• The Australian Government Department of Agriculture and Water

Resources has initiated a number of activities to build capability:

• Conducting a pest risk assessment

• Evaluating import measures for vectors

• Preparing an economic assessment of potential impact

• Planning a study tour to the United States

• Planning an regional symposium later in the year with international experts to share their experiences and knowledge

• Prioritising Xylella as a surveillance target for the 2016-17 national plant health surveillance program

• Preparing a contingency plan, through the Department of Economic Development, Jobs, Transport and Resources, Victoria

• States and territories maintain diagnostic capability and conduct

surveillance, and are prepared for an incursion

• Industries have in place a range of preparedness activities suited to their

needs and risks


Risk mitigation

• Control options

• Excluding vectors

• Removing infected plants and alternative hosts

• Planting tolerant/less susceptible plant varieties

• Dipping new stock with hot water - 50˚C for 45 minute

• Managing water stress

• What else can we do…

• On farm biosecurity and awareness

• Source plant material from high health schemes

• Report any suspicious symptoms

• Work with other industries

• Conduct surveillance - early warning is vital

• Research into appropriate control and management strategies


There are no treatments currently available to cure diseased plants in the field

For further information about Xylella fastidiosa, and other exotic plant pests, please see the following websites:

agriculture.gov.au/biosecurity

agriculture.vic.gov.au/agriculture/pests-diseases-and-weeds

planthealthaustralia.com.au

If you suspect a new plant pest, call the Exotic Plant Pest Hotline

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