Introduction to Bracket Fungus

Bracket fungi (also known as shelf fungi or polypores) are a diverse group of wood-decaying organisms that play an essential ecological role by recycling nutrients in forest ecosystems. However, when these fungi infect living trees — especially the iconic eucalypts of Tasmania, they can undermine the structural integrity of the wood, leading to safety risks in urban, residential, and park settings.

This guidance document provides a comprehensive overview of bracket fungi biology, identification, management strategies, and criteria for tree removal. It follows the requirements of Australian Standard AS4373-2007 (Pruning of Amenity Trees) and the Minimum Industry Standards(MIS) for arboricultural work, ensuring you have accurate, up-to-date advice tailored to Tasmanian conditions.

Mounting concern over tree failures during storm events has highlighted the value of proactive tree health monitoring.

What is Bracket Fungus?

Bracket fungi are characterised by their woody or leathery fruiting bodies—known as conks or brackets—that project horizontally from the tree trunk or large branches. Beneath the visible bracket lies a network of thread-like mycelium that penetrates the heartwood, the older, non-living inner core of the tree (Royal Horticultural Society[RHS], n.d.).

These fungi secrete enzymes that break down lignin and cellulose, the primary structural components of wood, allowing them to extract nutrients and energy.

The lifecycle of bracket fungi begins when spores land on a suitable substrate—often entering through wounds such as pruning cuts, storm damage, or bark abrasions. Once established, the mycelium can remain undetected for years, slowly colonising the heartwood. Fruiting bodies emerge when conditions support spore dispersal, indicating that significant internal decay has already occurred (McCaig, 2023).

Identification of common Tasmanian bracket fungi includes:-

• Ganoderma australe: large, brown to black woody brackets at the base or on roots, causing whiterot (Tasmanian Arboriculture Group,2024b).

• Fomitiporia robusta: hoof-shaped, layered brackets on wounds or stubs, lead to progressive whiteheart-rot (Tasmanian Arboriculture Group,2024a).

• Laetiporus portentosus: pale cream to beige brackets high on trunks, often indicating extensive upper heartwood decay (Australian National Botanic Gardens, n.d.).

Management Options

Inspection

Arrange for a qualified arborist to conduct a thorough risk assessment. This may include:

• Visual inspection for brackets, cracks, oozing sap or kino.

• Sounding the trunk with a mallet to detect hollow zones.

• Resistance drilling or sonic tomography to map internal decay (McCaig,2023).

Treatment

• Remove infected limbs at the branch collar using AS4373-2007-compliant cuts to facilitate compartmentalisation.

• Avoid leaving stubs that encourage further fungal entry. (Gardening KnowHow, 2020).

• No fungicidal treatments are effective against established heart rot. Efforts should focus on physical removal of decayed wood and maintaining overall tree vigour.

Cultural practices

• Minimise wounding: Protect trunks and roots from mechanical damage (e.g., mowers, vehicles).

• Mulching: Apply a 5–10cm layer of organic mulch over the root zone to conserve moisture and reduce soil compaction (Barry et al., 2001).

• Watering: Provide supplementary irrigation during prolonged dry spells to support tree health.

• Prune judiciously: Limit heavy canopy reductions, especially in wet conditions, which can create large wounds and encourage fungal invasion (Wardlaw et al., 2003).

When trees must be condemned & removed

Tree removal should be considered when one or more of the following criteria is met:

• Decay affects more than 50% of the remaining sound cross-sectional area of a critical trunk or limb (Tasmanian Arboriculture Group, 2024b).

• Bracket fungi are present at the base or root collar, indicating butt rot and a high risk of uprooting (Private Forests Tasmania,2020).

• The spread or growth rate of the fungus outpaces the tree’s natural ability to compartmentalise decay and heal wounds, meaning the tree cannot effectively wall off the advancing rot (Wardlaw etal.,2003).

• The tree is located in a high-target zone near buildings, roads, or public spaces, where failure could cause significant harm or damage.