Xylella Fastidiosa – What Do We Know and Are We Ready

Xylella fastidiosa: What do we know and are we ready? Suzanne McLoughlin, Vinehealth Australia. Xylella is a major threat due to its multiple hosts Suzanne McLoughlin, Vinehealth Australia’s (more than 350 plant species, many of which Technical Manager, analyses the grape and wine do not show symptoms), its multiple vectors community’s preparedness and knowledge about and its continued global spread. The pathogen Xylella fastidiosa, which is known to the industry causes clogging of plant xylem vessels, resulting as Pierce’s disease. This article first appeared in Australian and New Zealand Grapegrower and in water stress-like symptoms to distal parts of Winemaker Magazine, June 2017. the grapevine, with vine death in 1-2 years post infection (Figure 44). The bacterium is primarily Introduction transmitted in the gut of sapsucking insects and Xylella fastidiosa is a gram-negative, rod-shaped the disease cannot occur without a vector. bacterium known to cause Pierce’s disease in viticulture. Xylella fastidiosa was the subject of an While Xylella fastidiosa is known as Pierce’s international symposium held in Brisbane in May disease in grapevines, it is known as many other 2017, organised by the Department of Agriculture names in other host plants. It is inherently difficult and Water Resources (DAWR). A broad range of to control and there are no known treatments to international experts shared their knowledge and cure diseased plants. experience on Xylella with Australian federal and Xylella fastidiosa has been reported on various state government biosecurity personnel, as well host crops, either symptomatic or asymptomatic, as a small number of invited industry participants. in North America, Central America, South Xylella fastidiosa is considered one of the America, Canada, Iran, Taiwan, France, Germany, most harmful plant pathogenic bacteria in the Italy, Spain and Switzerland [as at 9 May 2017, world and causes death of infected plants. In according to the European and Mediterranean Australia, Xylella is our number one priority plant pest and it is a high priority pest for the Plant Protection Organisation (EPPO) Global wine industry. Neither Xylella fastidiosa, nor its Database https://gd.eppo.int/taxon/ XYLEFA/ highly efficient vector found in California, the distribution]. Xylella has not been detected in any glassy-winged sharpshooter (Figure 43), are Australian native plant species grown overseas. known to be in Australia. Xylella fastidiosa Xylella Figure 43. Glassy-winged sharpshooter. Photo courtesy of Reyes Garcia III, USDA Agricultural Research Figure 44. Bacterial leaf scorch caused by Xylella Service, Bugwood.org. fastidiosa. Photo: Vinehealth Australia. GRAPEVINE MANAGEMENT GUIDE 2018–19 | 61 The factors that must intersect for What constitutes preparedness? pierce’s disease to become a threat To be prepared to face a Pierce’s disease incursion Based on international experience in the fight that would threaten the Australian wine industry, against Xylella fastidiosa, a number of key factors we need to look inwardly as a government/ must intersect for Pierce’s disease to cause industry/research collective and ask ourselves a significant loss to the Australian wine industry. In range of tough questions such as: other countries, it has not simply been enough to • do we have a culture of strong leadership just have susceptible host plants, the pathogen ready or do we have an unco-ordinated, (Xylella fastidiosa) and available vectors (the ‘siloed’ approach to preparedness by system is a far more complex one as described government, industry and researchers in Figure 45). Four key factors are necessary with stakeholders unclear on roles and and must intersect each other, and a range of responsibilities? conditions pertinent to each key factor must also • what is our goal for management and be present to result in significant vine loss. In eradication in the short, medium and Australia, we therefore need to be alert but not long term, given our current capacity and alarmed. We need to use our time wisely to vastly capabilities, research status and available improve our preparedness capacity and capability technologies? to manage a potential incursion. Figure 45. Key factors for Pierce’s disease to be a threat to the Australian wine industry. 62 | Darren Fahey and Adrian Englefield – NSW DPI Development Officers Viticulture • do we have scheduled emergency response • what are our surveillance strategies for simulation activities? Are we recording results early detection and who is responsible and proactively addressing any weaknesses for their co-ordination? Do they differ for identified? symptomatic and asymptomatic hosts? Will • do we have a prioritised research and they be cross-sectoral? Have we mapped our extension framework developed by multiple land use cover, including riparian areas, in stakeholders with an agreed funding model sufficient resolution? How can we best use that outlines high priority activities key to our current technologies and what emerging preparedness? technologies could assist? • do we have readily available access to • do we have a range of effective management international resources and expertise? options in our toolkit to break the vector lifecycle and/or reduce vector populations • what does our pre-border, border and post- that have been discussed with industry? border quarantine management entail? Which of these if any will be mandated in the What zones will be put in place and what event of an incursion? movements will be allowed in and out? What disinfestation treatments will be required? • do we have the capacity within our nurseries to replace infected vines with less susceptible • what will the surveillance strategies be within varieties? these zones? Would industry representatives be required for surveillance as part of surge • will we offer compensation to growers for capacity following an outbreak? Would there vine losses and how would this be financed? be any additional foreseen imposition on • have we performed economic analyses nurseries as has occurred in California? on potential effects of an incursion on our • do we have a communications and awareness industry that have been ground-truthed by strategy for industry now and in the event of industry? an incursion? What have we learnt from the rest of • are we proactively training our personnel both the world? locally and internationally in field diagnosis, surveillance strategies, lab diagnostics and Some in-depth, practical presentations social science? were delivered at the symposium from the • do we have a clear understanding of xylem Californian and Italian viewpoints, outlining their sap-sucking insects already in Australia, which approaches to dealing with Xylella fastidiosa could potentially vector the Xylella fastidiosa incursions in predominantly grape and olive pathogen, and their host plant range? hosts. These are summarised below. • do we have readily available, internationally Californian example recognised, clear guidelines on field The Californian model for management of sampling? Pierce’s disease has been used as a blueprint in • do we have internationally recognised the United States to combat other high priority diagnostic protocols that minimise both false plant pests. It was realised early on that with positive and negative results? limited available research and the relative • which of our laboratories can test for Xylella strength of the glassy-winged sharpshooter fastidiosa Xylella fastidiosa and do we have sufficient surge vector, broad-scale disease eradication was not capacity available? possible in the short to medium term and that, therefore, vector management was the key. • can we successfully conduct strain typing and how long does this take? Do we have a rapid, Collaboration has been imperative; between accurate, cost-effective in-field diagnostic federal, state, regional, local council regulatory technique which could negate the need and extension staff, multiple industries, to move potentially infected material for researchers, nurseries and the public, with diagnosis? roles and responsibilities documented and understood by all parties. A strong emphasis on communication and awareness strategies GRAPEVINE MANAGEMENT GUIDE 2018–19 | 63 ensured that the effectiveness of management Italian example measures were constantly ground-truthed. This The Italian approach to surveillance for Xylella approach avoided negative social backlash, fastidiosa in olives in the Apulia region presented especially from treatment programs, and even a strong use of technology and an integrated incorporated visits to local schools. track and trace system for sample collection Understanding the vector lifecycle was crucial. from the field to the laboratory. Much of the Due to the nature of the vector, area-wide, technology presented mirrored Australia’s cross-sectoral vector management was needed, current capacity in pockets, but highlighted involving treating the vector in citrus as the our lack of co-ordinated national geographic alternative host where it overwinters, before information system and remote sensing system moving into grapes as the primary host, causing capability necessary in the event of a cross- Pierce’s disease. Multi-faceted trapping and border incursion. monitoring programs were established to Surveillance activities focus on three designated determine the boundaries of the vector’s location. quarantine zones; the infected area bounded by Federal and state quarantine regulations were a 20

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