Armillaria luteobubalina: Dealing with Honey Fungus in Tasmania

Have you detected a honey-coloured mushroom growing on your property? Does it appear near or at the base of a seemingly healthy tree? If so, there’s a chance your tree is battling Armillaria luteobubalina.

Armillaria luteobubalina, or Australian honey fungus, is the most widespread of the six Armillaria species found in Australia. As an endemic pathogen, Australian honey fungus attacks and kills the roots of susceptible trees and shrubs, causing root rot. Whether you know it as honey fungus, honey mushroom or bootlace fungus, Armillaria is not good news for your property.

In recent years, reports of Australian honey fungus killing trees in urban parks and gardens have increased. If left untreated, affected trees can develop Armillaria Root Disease (ARD), which can be fatal for your trees.

In this article we will answer: 

• How do I identify Australian honey fungus?
• What are the symptoms of an Australian honey fungus infection?
• I think my tree has Australian honey fungus. Should I be worried?
• Treatment for Australian honey fungus.
• Tasmanian Tree Care: How we can help
  

How do I identify Australian honey fungus?

The first visible signs of Australian honey fungus are generally seen in autumn, when clusters of mushrooms appear at or near the base of infected trees. These fruiting bodies can even appear away from the base of the tree, just above infected roots (see images below). 

Australian honey fungus is distinguishable by its yellow to honey-brown colour and pinkish/yellowish gills. For a more detailed description, click here to view our Armillaria Fact Sheet. 

In addition to the recognisable yellow mushroom, you may also find a creamy-white fungal mass under the bark of infected areas. Some species of Armillaria produce rhizomorphs: A cord or “bootlace” structure created by the fungi. Old rhizomorphs appear black while younger threads appear red-brown with a white tip.

Symptoms of an Australian honey fungus infection

Typically trees will appear healthy until reaching advanced stages of infection, where they may experience:

– Stunted leaves
– Wilted foliage
– Reduced growth
– Branch dieback

I think my tree has Australian honey fungus. Should I be worried?

Unfortunately, Australian honey fungus can be fatal for your tree. What’s worse, the fungus can spread to other trees within your property if left untreated. 

Some species, however, are more resistant than others. These include: 

– European ash (Fraxinus excelsior)
– Wilga (Geijera parviflora)
– Sweetgums (Liquidamber)
– London plane (Platanus x hispanica)
– Black locust (Robinia pseudoacacia)
– Lindens Tilia sp.

Research shows seedlings and saplings are most susceptible to the fungus, while healthy established trees (generally older than about 20 years) are more resistant.  

Treatment for Australian honey fungus

While Australian honey fungus plays an important role in healthy forests and woodlands, untreated cases in urban areas can kill trees and spread throughout your property.  

If you suspect your tree is infected, having it professionally treated is the best course of action. As experienced arborists, Tasmanian Tree Care can accurately assess your tree and identify the best way forward. 

Catching Australian honey fungus early increases the chances of successful treatment, as completely removing the fungus is difficult and cannot always be guaranteed. Typically, the best option is to remove all woody material from the infected tree, including the roots. Any infected debris should be disposed of, and woodchips should not be used as mulch.

This treatment, however, can also disrupt the tree’s relationship with beneficial fungus. Weighing this risk against the benefit of treatment is imperative. 

If all the infected elements cannot be removed, we may recommend the installation of root barriers. Typically placed .5m – 1m deep, root barriers stop the fungus spreading to non-infected areas around the tree. Understandably, the effectiveness of this treatment depends on the degree and spread of the fungus. 

To stem the spread of the infection on your property, infected trees and soil can be removed and replaced with clean soil. To ensure the breakdown of the fungus, it is recommended that no trees are replanted for up to 12 months. During this time, adding compost and organic matter to the site will encourage the decomposition of any fungus left behind. 

At which stage, Tasmanian Tree Care can help you decide on replanting a species of tree that is more resistant to the fungus. 

How we can help

Tasmanian Tree Care provides professional solutions to Australian Honey Fungus for any commercial or residential property. If you’re unsure about the health of your natural assets, please contact us to organise an assessment. It’s true what they say: prevention is better than a cure.

Images curtesy of the Mushroom Observer, a source for mycological images.

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