Biosecurity tool-set: optimising quarantine zones for eradication through consideration of Australia’s success with plant pathogen eradications in horticulture

Plant pathogen eradication programs can be both expensive and cause social conflicts due to restrictions imposed within quarantine zones (QZs) and significant potential damage to host populations in agricultural, residential, urban and semi-natural environments. The optimisation of QZs, particularly destruction zones, is therefore highly desirable to improve the efficiency of containment and minimise negative impacts of eradication programs. Knowledge gained from previous eradication programs in Australia can be useful for identifying the factors and issues that influence pathogen containment, particularly the effectiveness of QZs. This study therefore examined the influence of features of disease outbreaks on pathogen containment using several past programs launched to eradicate exotic plant pathogens in horticulture as case studies. Australia has had considerable success in eradicating serious horticultural pathogens over the past 100 years. Eradication programs of ten horticultural plant pathogens were reviewed, most of which were successfully eradicated. The most important factor for success was that the QZ be as large as practicable while delimitation activities are taking place. Once the size of the incursion is known and eradication is considered feasible, the size of the pest quarantine areas and destruction zones should be informed foremost by the pathogen biology and behaviour, plus consideration of location, topography and host prevalence. Some diseases such as citrus canker, grapevine leaf rust and black Sigatoka required large destruction zones, tens of km in radius, while others such as angular leaf spot and potato spindle tuber viroid required very small destruction zones of several m in radius. This review also demonstrated the value of flexibility to revise the QZs accordingly as eradication progresses and the importance of commitment to eradicate by all parties. The information identified will be useful to further strengthen the containment of plant pathogens in different incursion settings in Australia.