Uredo rangelii
| Uredo rangelii | |
|---|---|
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| On Eugenia reinwardtiana | |
| Scientific classification | |
| Kingdom: | Fungi |
| Division: | Basidiomycota |
| Class: | Pucciniomycetes |
| Order: | Pucciniales |
| Family: | Incertae sedis |
| Genus: | Uredo |
| Species: | U. rangelii |
| Binomial name | |
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Uredo rangelii J.A.Simpson, K.Thomas & Grgur. (2006) |
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Uredo rangelii, commonly known as myrtle rust, is a fungal plant pathogen native to South America that affects plants in the family Myrtaceae. It is a member of the fungal complex called the guava rust (Puccinia psidii) group. The spores have a distinctive yellow to orange colour, occasionally encircled by a purple ring. They are found on lesions on new growth including shoots, leaves, buds and fruits. Leaves become twisted and may die. Infections in highly susceptible species may result in the death of the host plant.
As of late 2013, it is infecting around 179 species in New South Wales and Queensland, from 41 genera (around 46% of genera in the Myrtaceae) in Australia.
The rust was first described scientifically in 2006 by mycologists J.A. Simpson, K. Thomas, and Cheryl Grgurinovic.
Myrtle rust is typically characterised by the appearance of urediniospores on the underside of the leaf, though urediniospores may also be found on the top of the leaf or on young stems. Initially, the disease appears as small purple or red brown flecks with a faint chlorotic halo on the leaf surface, which coalesce to form bright yellow pustules. As the rust develops, these pustules often fade to a grey brown colour. A high degree of pustule coalescence can result in distortion of the leaf. Myrtle rust also makes plants more susceptible to secondary infections, which may occur within days of the initial appearance of the pustules.
Favourable conditions that increase the infection rate include: new tissue; high humidity; free water on plant surface for more than 6 hours; moderate temperatures, around 15–25 °C. Low light conditions (minimum of 8 hours) after spore contact can increase germination.
The main ways in which myrtle rust can be spread are by: the movement of infected plant material, the movement of contaminated equipment, wind, water and gravity, animals, humans and/or vehicles.
Myrtle rust may remain on a single host plant to complete its life cycle, which can be as short as 10–14 days.
Myrtle rust was first recorded in Australia in mid-2010 and currently poses a major threat to the continent's ecosystem given that almost 80 per cent of Australian native trees are Mytraceae, most indigenous species rely on healthy trees for their survival. Additionally it poses a major threat to Australia's primary industry sector. Its current range includes much of the eastern coastal fringe of the Australian mainland.
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Wikipedia