How to identify White rot fungus

To correctly identify White rot fungus (Phlebia tremellosa), check each of these features in order. Misidentification is the most common cause of mushroom poisoning, so cross-reference multiple sources.

Step-by-step identification

1. 1

   Cap

   Shape, color, surface texture, and diameter.

   When present as a reflexed margin, the 'cap' is typically 1-5 cm wide and projects 1-3 cm from the substrate. It is fan-shaped to semicircular, thin, and leathery. The color ranges from white to cream, sometimes with pale ochre or brownish zones. The surface is finely hairy or velvety, especially when young, becoming smoother with age. The margin is often wavy or lobed.

2. 2

   Gills

   Attachment to stem, color, and spacing.

   The hymenial surface is not true gills but rather a system of intricate, labyrinthine, or gill-like folds (lamellae or merulioid folds). These folds are typically 1-3 mm deep, white to cream, sometimes with a pinkish or yellowish tint, and often radially arranged. They are soft and somewhat gelatinous when fresh, becoming more rigid upon drying.

3. 3

   Stem

   Length, shape, surface, and any ring.

   Absent. The fruiting body is sessile, growing directly on the substrate.

4. 4

   Flesh

   Color, texture, and bruising reaction.

   The flesh is thin, tough, and leathery, white to cream in color. It is not easily broken.

5. 5

   Fruiting body

   Overall growth pattern.

   The fruiting body is typically effused-reflexed to resupinate, meaning it grows flat against the substrate with a reflexed (turned-up) margin, or entirely flat. It can also form small, fan-shaped to semicircular brackets. The upper surface (when reflexed) is usually white to cream, often hairy or finely tomentose, and may have concentric zones. The underside (hymenial surface) is distinctive, featuring a network of gill-like folds or labyrinthine pores, which are white to cream, sometimes becoming yellowish or ochraceous with age. These folds are often radially arranged.

6. 6

   Habitat

   Where it grows and on what substrate.

   Saprobic on dead deciduous wood, less commonly on conifers. It causes a white rot, breaking down both cellulose and lignin. It is often found on fallen logs, branches, and stumps, particularly in damp, shaded areas of forests.

Key Facts

Cap surfaces

Hairy to finely tomentose, white to cream, sometimes zoned.

Growth Form

Effused-reflexed to resupinate, sometimes forming small brackets.

Spore Print

White

Body color

White to cream, sometimes with yellowish or pinkish tints on the hymenial surface.

Odor

Mild, indistinct.

Flesh bruises

Does not bruise significantly.

Height

Not applicable (sessile)

Cap Diameter

When reflexed, individual caps are typically 1-5 cm wide, projecting 1-3 cm.

Fruit body characteristics

• Gill attachment: Not applicable (hymenial surface is labyrinthine/merulioid folds, not true gills)
• Stem shape: Absent
• Stem surface: Absent
• Ring: Absent
• Stem cross-section: Absent

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