Myrtle rust: current and future impacts on myrtaceous diversity in Australia

Puccinia psidii has long been considered a signifi cant threat to Australian plant industries and ecosystems. In 2010, P. psidii was detected for the fi rst time on the central coast of New South Wales, spreading rapidly to become widespread on the east coast of Australia. Our studies aimed to determine the host range and impact of P. psidii on species of environmental signifi cance. Thehost range of P. psidii in Australia has increased rapidly, with fi eld surveys identifying more than 220 host species from 51 different genera of Myrtaceae. Puccinia psidii has now been identifi ed from many different native Australian forest ecosystems including coastal heath, coastal and river wetlands, sand islands, and littoral, montane, subtropical and tropical rainforests. The impact of P. psidii on individual trees and shrubs has ranged from minor leaf spots to dieback and reduced fecundity. Tree death as a result of repeated infection has also been recorded for some species, with regenerating seedlings becoming infected and killed by P. psidii. Puccinia psidii infection has been recorded on fl ower buds, fl owers, and fruits of 28 host species. The full impact of this disease in Australia may not be realised for some years