How to identify Milk-white Toothed Polypore

To correctly identify Milk-white Toothed Polypore (Irpex lacteus), 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 effused-reflexed, the cap-like margin is narrow, typically 0.5-2 cm wide, and semicircular to irregular. The upper surface is finely tomentose to strigose (hairy), white to cream, sometimes becoming grayish or greenish with age due to algae. The margin is often thin and wavy.

2. 2

   Gills

   Attachment to stem, color, and spacing.

   Not a gilled mushroom. The hymenophore (fertile surface) is initially poroid (pore-like) but quickly develops into an irpicoid (toothed or labyrinthine) structure. The teeth are flattened, irregular, and often fused, appearing like flattened spines or ridges. They are white to cream, becoming yellowish or brownish with age or when dried. The teeth are typically 1-5 mm long.

3. 3

   Stem

   Length, shape, surface, and any ring.

   Absent. This fungus grows directly on the substrate.

4. 4

   Flesh

   Color, texture, and bruising reaction.

   The context (flesh) is thin, tough, fibrous, and white to cream-colored. It is not easily separable from the substrate.

5. 5

   Fruiting body

   Overall growth pattern.

   The fruiting body is typically resupinate (lying flat on the substrate) to effused-reflexed (partially resupinate with a projecting cap-like margin). It can be quite variable in shape, often forming irregular patches that can be several centimeters to tens of centimeters long and wide. The thickness is usually 1-5 mm. The upper surface, when present (effused-reflexed form), is finely hairy to velvety, zonate or azonate, and white to cream or pale yellowish, sometimes with greenish algal growth.

6. 6

   Habitat

   Where it grows and on what substrate.

   Saprobic on dead hardwood logs, branches, and stumps. Occasionally found on conifers, but predominantly on deciduous trees. It causes a white rot.

Key Facts

Cap surfaces

Finely tomentose to strigose (hairy) when effused-reflexed; otherwise absent.

Growth Form

Resupinate to effused-reflexed, often forming extensive patches.

Spore Print

White.

Body color

White to cream, sometimes yellowish or grayish with age.

Odor

Indistinct.

Flesh bruises

Does not bruise significantly; may yellow slightly with age or drying.

Height

Not applicable (resupinate/effused-reflexed).

Cap Diameter

Not applicable (resupinate/effused-reflexed); individual reflexed margins typically 0.5-2 cm wide.

Fruit body characteristics

• Gill attachment: Not applicable (no gills).
• Stem shape: Absent.
• Stem surface: Absent.
• Ring: Absent.
• Stem cross-section: Absent.

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