The plant pathogenic bacterium Xylella fastidiosa causes Pierce's disease in grapevines as well as various other crop diseases. Though not detected in Australia it has spread internationally so poses a significant biosecurity risk to Australia. The host status of 12 Australian native plant species was assessed in California using mechanical inoculations and re-isolation of the pathogen after an overwintering period to determine seasonal persistence of the bacterium. Leptospermum laevigatum (Gaertn) F.Muell., Swainsona gaeligifolia (Andrews) R.Br., G. alpina Lindl. and Hakea petiolaris Meisn supported X. fastidiosa . The average pathogen population was 1.6 Ã— 10 5 colony forming units/g of plant material in S. galegifolia , 5.4 Ã— 10 4 colony forming units/g in H. petiolaris and could not be determined in L. laevigatum or G. alpina due to difficulty culturing. Systemic movement of the pathogen to a point 10 cm distal to the site of inoculation occurred in all four of the Australian native species that tested positive for the pathogen . Results are discussed in relation to preparedness for a likely incursion into Australia of the bacterium, a biosecurity event that would require a rapid and targeted response.