Austropuccinia psidii added again to the EPPO Alert List
Why: Austropuccinia psidii, causing myrtle rust, was added to the EPPO Alert List (as Puccinia psidii) in 1998 and removed in 2003 as a Pest Risk Analysis concluded that the risk was low for the EPPO region. However, since then, the fungus has established in areas with a climate more similar to the climate of the EPPO region, significantly increased its host range, and recent interceptions indicate that it can move in trade with plants for planting. In addition, new aggressive races of A. psidii have been observed. The Panel on Phytosanitary Measures considered that it should be added again to the Alert List to raise awareness among NPPOs.
Where:
A. psidii is considered to be native from South America.
Africa: South Africa.
Asia: China (Guangdong, Hainan), Indonesia (Java, Sumatra), Japan, Singapore.
North America: Mexico, United States of America (California, Florida, Hawaii).
Central America and Caribbean: Costa Rica, Cuba, Dominica, Dominican Republic, Guatemala, Jamaica, Panama, Puerto Rico, Trinidad and Tobago, Virgin Islands (British), Virgin Islands (US).
South America: Argentina, Brazil (Amapa, Bahia, Espirito Santo, Minas Gerais, Parana, Pernambuco, Rio de Janeiro, Rio Grande do Sul, Santa Catarina, Sao Paulo), Colombia, Ecuador, Paraguay, Uruguay, Venezuela.
Oceania: Australia (New South Wales, Northern Territory, Queensland, Tasmania, Victoria), New Caledonia, New Zealand.
On which plants: A. psidii infects over 500 species in the Myrtaceae family. This includes numerous native species in Oceania, as well as commercially important species for wood production (e.g. Eucalyptus spp.), for fruit production (e.g. Acca sellowiana, Psidium guava) or as ornamentals (e.g. Callistemon, Eugenia, Melaleuca, Syzygium). Myrtus communis, the sole Myrtaceae species native to Europe, and an important component of vegetation in Mediterranean regions, was recently shown to be a host.
Damage: A. psidii infects young leaves, shoot tips and young stems. Fruit and flower parts are also susceptible. The first signs of rust infection are tiny spots or pustules which then evolve to form distinctive yellow pustules. The disease can cause deformed leaves, heavy defoliation of branches, dieback, stunted growth and even plant death.
Dissemination: Urediniospores of A. psidii can be wind-dispersed over long distances. Spores can also be dispersed by animals (e.g. birds, bats, insects). Viable spores have been detected on clothing, personal effects, and equipment following visits to rust-affected plantations. In trade, infected plants for planting are considered as a pathway of introduction into new areas. The potential introduction with wood is not clear.
Pathways: Plants for planting, cut foliage, wood?
Possible risks: A. psidii has caused significant impacts in Eucalyptus plantations in Brazil and in natural ecosystems in Oceania. Once introduced into an area, it has proved impossible to eradicate. In the EPPO region, hosts plants are grown for wood and ornamental purposes, and M. communis is an important species in Mediterranean ecosystems. There is uncertainty on the climatic suitability of the whole EPPO region for the establishment of the fungus but it seems advisable to prevent its introduction.
Sources
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