From the 2016 Plant Biosecurity CRC Science Exchange: Invasive pests and pathogens can have devastating and unpredicted impacts on native ecosystems. The threat that Puccinia psidii (myrtle/eucalyptus/guava rust) posed to Australian industries was well recognised, but until its introduction in 2010, there was scant consideration of the impacts this disease may have on endemic Myrtaceous plant species and associated communities in native environments. Since its detection in Australia, the distribution and host range of P. psidii has rapidly expanded and entire species and plant communities are now under threat. The risk myrtle rust poses to threatened Myrtaceae species is becoming more apparent with significant dieback and tree death recorded as a result of repeated infection. The impact of myrtle rust has also significantly affected industries reliant on Myrtaceae including nursery and garden and the developing lemon myrtle industry. The research being undertaken into myrtle rust has enabled improved species selection for production and retail nurseries, and for urban tree planting. It has provided disease screening and assessment methodologies for determining species and plant community impacts and selection of resistant material for industry and environmental benefit. Data collected has identified species at risk of extinction and plant communities in decline as well as identified individuals or populations showing levels of resistance that could be used for future conservation or regeneration programs. The data are also being used for legislative listing of species and as support evidence for declaring myrtle rust a Threatening Process. More broadly it has highlighted the vulnerability of Australian native ecosystems to the threat of invasive pests and pathogens. Speakers: Geoff Pegg and Bob Makinson