Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

National surveys did not detect Erwinia amylovora on host plants in Australia.

Abstract

The report of the presence of E. amylovora in the Royal Botanic Gardens, Melbourne (RBGM) by New Zealand authorities in May 1997 triggered one of the most extensive quarantine surveys in Australia. After three years, surveys have failed to confirm the presence of fire blight. The initiative was planned and funded by national coordination between the Commonwealth and State governments of Australia. Targets were commercial orchards and host plants in nurseries, parks and gardens. In orchards, sampling methods were designed to ensure a 99% level of certainty that fire blight symptoms would be detected at a 0.1% infection level. Surveys were timed to coincide with petal fall of the last flowering cultivar. All host plants in nurseries were inspected during spring and early summer. Urban surveys were commissioned in Melbourne and Adelaide as well as in provincial towns across Australia by examining the nearest host plant on a 1, 2 or 5 kilometre grid pattern. An estimated 6.5 million orchard trees, 1.3 million host trees in nurseries and over 8500 plants in urban environments were surveyed in the autumn and spring of 1997. Similarly, an estimated 2.9 million plants were examined in 1998 and 1999. Where suspicious symptoms were found, samples were taken and tested for E. amylovora using a nationally approved diagnostic protocol. Between autumn 1997 and spring 1999, more than 620 samples were taken from plants that showed possible symptoms of fire blight. Diagnostic tests showed that E. amylovora was not detected from any of these samples. However, a number of colonies with characteristics similar to E. amylovora were isolated on selective media. The full suite of diagnostic tests confirmed that these isolates were not E. amylovora. Investigations are continuing to identify these bacteria and understand their biology.