Wood-Decaying Fungi In Tasmania: Fomitiporia Robusta

This fungus is known for causing white rot in trees, including blue gum (Eucalyptus globulus) and stringy bark (Eucalyptus obliqua) in Tasmania.

In this article we will investigate Fomitiporia robusta’s…

• Taxonomy
• Morphology
• Life cycle
• Ecology
• Management
• How can we help?

Taxonomy:

Fomitiporia robusta was first described as Phellinus robustus by Berkeley and Broome in 1880. Later, in 2019, it was reclassified as Fomitiporia robusta based on the phylogenetic analysis of DNA sequences. F. robusta belongs to the Fomitiporia clade, which is a group of wood-decaying fungi characterized by a brown to black, perennial, and woody fruiting body that is hard and woody.

Morphology:

Fomitiporia robusta has a perennial fruiting body that is hoof-shaped and can grow up to 30 cm in diameter. The upper surface of the fruiting body is rough, hard, and dark brown to black, while the lower surface is white to cream-colored with small, round pores. The flesh of the fruiting body is woody and brown. The spores of F. robusta are hyaline, cylindrical, and measure 4-6 x 2-2.5 μm. The basidia are club-shaped and have four spores. The mycelium is white and grows in the heartwood of the tree, causing white rot.

Life Cycle:

The life cycle of Fomitiporia robusta begins with the germination of spores on the bark of a host tree. The spores then penetrate the bark and colonize the sapwood, where they grow and spread to the heartwood. The fungus then starts to break down the lignin and cellulose in the wood, causing white rot. The fungus produces enzymes, such as laccase, manganese peroxidase, and lignin peroxidase, which break down the lignin in the wood. This process results in the formation of a white spongy substance in the secondary tissues in the heart of the tree, similar to white bread.

Ecology:

Fomitiporia robusta is a pathogen that affects blue gum (Eucalyptus globulus) and stringy bark (Eucalyptus obliqua) in Tasmania. It colonizes these trees through pruning wounds or wounds from mechanical damage. The fungus is able to effectively decay and heartwood of the tree, often leaving the tree structurally weakened. F. robusta is also known to cause decay in other eucalypt species, including Tasmanian black gum (Eucalyptus ovata) and swamp gum (Eucalyptus regnans).

Management:

There is no effective treatment for Fomitiporia robusta, and infected trees eventually have to be removed for safety reasons if they are in an area with high occupancy. More often then not, the tree will react to the infection and put in increased callus growth arounf the woud in an effort to compartmentalise.  This is effectively a race between decomposition and reactive growth.  Regardless, if the tree is in an area with occupancy and not in a natural bush setting, it should be subject to regular risk assessments.

The best way to manage this fungus is through preventative measures. These include avoiding wounding the tree, minimise the size of pruning cuts, minimise damage from other activities such as machinery movements and maintaining the tree’s overall health.

Fomitiporia robusta is a wood-decaying fungus that causes white rot in trees, including blue gum (Eucalyptus globulus) and stringy bark (Eucalyptus obliqua) in Tasmania and often leads to reduction in structural integrity.

How Can We Help?

Tasmanian Tree Care and it’s highly trained arborists can identify potentially harmful fungi in your garden or property. If you’re unsure about the health of your natural assets, please contact us to organise an assessment.

Images courtesy of The Mushroom Observer, Jerzy Opioła via WikiMedia.