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How to Manage Myrtle Rust and Phellinus Noxius

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Tree diseases are a problem amongst many species of natural flora in Australia. Some of them are easily treated and do not cause too many problems, but other diseases can cause many issues for the eco system and the amenity of landscapes. This is why it’s important that we all take a closer look at our plants and management practices in order to help prevent the ongoing spread of tree diseases.

Two tree diseases we are commonly faced with in South East Queensland are Myrtle Rust and Phellinus Noxius, so here we’ve taken an in-depth look at what they are, including some preventative measures.  

Myrtle Rust

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Image courtesy of Creative Commons: Casliber

What is Myrtle Rust?

Myrtle Rust (uredo rangelii), or Eucalyptus Rust as it is sometimes referred to as, is a fungal disease. It predominantly affects the Myrtaceae family, Callistemons, Leptospermums, Melaleucas and Angophoras. It is most commonly found in Eucalyptus trees, Lilly Pilly’s, and Bottle Brush shrubs.

Where has it originated from?

It is believed to be a South American disease, and possibly migrated here through spores on travellers between the countries.

Where is it found in Australia?

The majority of cases are along the eastern seaboard of Australia, from the south of New South Wales right through to Northern Queensland. There have been some cases in Victoria and metropolitan Melbourne, and there was also a case found quite recently in February 2015 in Tasmania. The growing area is cause for concern, as it may suggest that it is rapidly spreading to natural country regions.

How is it identified?

Myrtle Rust is quite distinguishable. It starts with purple coloured blotches on the leaves of trees that are affected. Normally within 14 days and weather dependant, these blotches then become yellow spores. This egg yolk-like coloured spore is what makes it easier to spread to other trees, and the yellow spores continue to spread across to more leaves on the tree. This then leads to deformation of the leaves, heavy defoliation of the branches, stunted growth, and eventually leads to death.

This disease will often attack new growth in trees, making young trees susceptible to it. It also hinders new growth after an event such as a bushfire. After a bushfire, new leaves, branches and sprouts will emerge with a higher potential of being attacked. If the disease makes its way to this new growth, it can easily destroy the tree.

How is it spread?

Myrtle Rust can spread easily due to it’s yellow spores which are easily passed on via the wind. However, it can also spread on animals that move from a contaminated tree to one that is not. Garden tools that have worked on a tree with the disease and which are then used on a non-contaminated plant can make the non-infected tree susceptible to the disease. Therefore, it’s quite important to ensure all tools are properly cleaned of any of the spores before moving onto other plants and gardens.

Even clothing and shoes can move the disease to other areas, and another way it can spread is by moving contaminated trees and branches into new areas that do not have the disease. That is why it’s quite important for commercial nurseries to check on the health of their trees and plants before moving plants into other states and areas.

What needs to be done if there is Myrtle Rust on your plants?

There are several steps that need to be taken when dealing with an infection of Myrtle Rust. Some people will try to spray the affected plant with fungicide, but because the plant is more than likely to die of the disease it’s more common to remove the plant entirely. Many people will either remove just the affected tree, while others will remove adjacent trees as well as a precautionary action. However, the trees cannot be simply added to green waste, as it can often still spread this way.

The best way to manage an infected tree is to remove it completely and store it in bags for several weeks in the sun. This is to make sure the disease can be contained, and will start to kill it off. This bag then needs to be sent to landfill where it can be buried. This is to stop it from continuing to spread to other plants in the immediate area, and in the green waste disposal areas.

Phellinus Noxius

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Image courtesy of Creative Commons: Million Moments

What is Phellinus Noxius?

Phellinus Noxius, or Brown Root Rot as it is sometimes referred to, is a fungal disease found in trees. It has a wide range of host trees of more than 200 species, but the majority of trees affected are figs, poinciana tree, leopard tree, avocado, and hoop pines.  It destroys the tree by attacking the root system, which then cuts off nutrient supply to the tree. The tree begins to weaken due to lack of nutrients and eventually dies.

Where has it originated from?

It is found in Southeast Asia, Africa, Oceania, Japan, Central America, and the Caribbean. It is found naturally in subtropical and tropical rainforest areas, however there have also been cases in sand dune areas and dry inland tree species.

Where is it found in Australia?

First identified in Australia around 1952, it is predominantly found along the east coast of the country from Cape York to northern New South Wales.

How is it identified?

One of the easiest ways it can be identified is by the stocking that takes form along the roots and base of the tree near decaying regions. The stocking has a white border which normally turns brown as the disease progresses along the tree, and it will continue to advance up the trunk. Leaves, sticks and soil will also adhere to the Phelllinus Noxius stocking, however not all trees with Phellinus Noxius will display stocking symptoms above ground level.

Mycelial felt is often displayed between the bark and the wood of the tree. This is a white substance that literally looks felt-like in texture. It will appear to be layered between the parts of the tree.

How is it spread?

It has been suggested that the brown root rot is spread via root to root contact. Where a tree is infected, its root system touching another non-infected tree will often allow the disease to spread to neighbouring trees. Roots of healthy trees contacting with infested woody material in the soil has the potential to attract the disease.

Infested soil can stay contaminated for many years, so it’s important to ensure no other trees are planted within the infected soil areas for quite some time. In fact, it is believed the soil can stay contaminated for up to 50 years.

What needs to be done if there is Phellinus Noxius on your tree?

As the disease can appear in urban and city gardens, it may appear in your backyard. To enable correct  treatment for this disease it is imperative to obtain correct advice from a qualified arborist who will take samples for testing for positive identification. 

To reduce the spread to other trees in the area, installing root barriers beyond the live dead margin in an attempt to stop other trees nearby growing into the infected area, can largely assist. So far, there are no chemical control measures for this particular fungal disease, and the recommended way of controlling it is by removing heavily affected trees.

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