Milk-white Toothed Polypore

(Irpex lacteus)

Conservation Status
Milk-white Toothed Polypore
  IUCN Red List

not listed


not listed


not listed


Milk-white Toothed Polypore is widespread in Europe and North America. It is very common in the eastern United States to the Midwest, including Minnesota, but rare in the Southwest. It grows flat (resupinate) on the bottom and sides of logs and fallen branches of hardwood trees, infrequently also on conifers. It usually obtains its nutrients from dead wood (saprobic), possibly also from live cherry wood (parasitic). It is exceptionally resistant to pollution toxicity.

The fruiting body is a patch of pore surface spread out flat (effused) on a branch or log (substrate). It is dry, stiff, and white, off-white, or cream-colored. Adjacent patches often fuse together creating a long row. There are 2 or 3 pores every thirty-second of an inch (1 mm). The pore walls are thin and disintegrate unevenly. As the walls break down the spore surface becomes maze-like. Eventually, only flattened, tooth-like projections less than ¼ (6 mm) long remain. When growing on the side of a log or branch it may develop shelf-like caps. If present, the cap is to 1½ wide, whitish to grayish, often concentrically zoned, and densely covered with velvety hairs. There is no stem. The flesh is thin and tough. It is not edible.


Similar Species

Habitat and Hosts

Dead hardwood logs and branches




Annual but persists year-round


Distribution Map



4, 7, 24, 26, 29, 30, 77.




Widespread and very common

  Kingdom Fungi (fungi)  
  Subkingdom Dikarya  
  Division Basidiomycota (club fungi)  
  Subdivision Agaricomycotina (jelly fungi, yeasts, and mushrooms)  
  Class Agaricomycetes (mushrooms, bracket fungi, puffballs, and allies)  
  Subclass Agaricomycetidae  
  Order Polyporales (shelf fungi)  
  Family Irpicaceae  
  Genus Irpex  

There is wide disagreement about the family to which the genus Irpex belongs. NCBI places it in Irpicaceae, Fungi Growing on Wood (Gary Emberger, Messiah College) in Phanerochaetaceae, Encyclopedia of life in Polyporaceae, MushroomExpert in Steccherinaceae, and until 2019, Index Fungiforum placed it in Meruliaceae. Index Fungiforum very recently transferred Irpex to the family Irpicaceae.




Boletus cinerascens

Boletus tulipiferae

Coriolus lacteus

Coriolus tulipiferae

Daedalea diabolica

Hirschioporus lacteus

Hydnum lacteum

Irpex bresadolae

Irpex diabolicus

Irpex hirsutus

Irpex lacteus

Irpex pallescens

Irpex sinuosus

Irpiciporus lacteus

Irpiciporus tulipiferae

Microporus chartaceus

Microporus cinerascens

Polyporus chartaceus

Polyporus tulipiferae

Polystictus bresadolae

Polystictus chartaceus

Polystictus cinerascens

Polystictus cinerescens

Polystictus tulipiferae

Poria cincinnati

Poria tulipiferae

Sistotrema lacteum

Steccherinum lacteum

Trametes lactea

Xylodon bresadolae

Xylodon hirsutus

Xylodon lacteus

Xylodon pallescens

Xylodon sinuosus


Common Names


Milk-white Toothed Polypore










In fungi: referring to the fruiting body lying flat on the surface of the substrate, without a stalk or a cap.



Obtaining nutrients from non-living organic matter, such as decaying plant or animal matter.

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    Milk-white Toothed Polypore      


    Milk-white Toothed Polypore   Milk-white Toothed Polypore  
    Milk-white Toothed Polypore   Milk-white Toothed Polypore  
    Milk-white Toothed Polypore   Milk-white Toothed Polypore  
    Milk-white Toothed Polypore   Milk-white Toothed Polypore  
    Milk-white Toothed Polypore   Milk-white Toothed Polypore  
    Milk-white Toothed Polypore   Milk-white Toothed Polypore  
    Milk-white Toothed Polypore   Milk-white Toothed Polypore  
    Milk-white Toothed Polypore      



  Irpex lacteus
Amadej Trnkoczy
  Irpex lacteus  

Album description

Irpex lacteus (Fr.; Fr.) Fr. Elench. Fung. p145, 1828, syn.: Sistotrema lacteum Fr.
Milk-white toothed polypore, DE: Milchweisser Eggenpilz
Slo.: belkasti rašpovec

Dat.: Feb. 23. 2014
Lat.: 46.35947 Long.: 13.70424
Code: Bot_784/2014_DSC0038
File names: from to


Dat.: Feb. 27. 2014
Lat.: 46.35947 Long.: 13.70424
Code: Bot_786/2014_DSC0132
File names: from to

Habitat: alpine valley, an opening in mixed forest with predominantly Fagus sylvatica followed by Picea abies; modestly inclined southeast oriented mountain slope, overgrown calcareous ground composed of scree, rocks and boulders; mostly in shade, partly protected from direct rain by tree canopies; average precipitations ~ 3.000 mm/year, average temperature 7-9 deg C, elevation 560 m (1.950 feet), alpine phytogeographical region.

Substratum: cut down trunk of Fagus sylvatica lying on ground, in its late initial phase of integration; the trunk was massively infected also with Trametes hirsutum.

Place: Lower Trenta valley, between villages Soča and Trenta, right bank of river Soča, near 'Na melu' place, East Julian Alps, Posočje, Slovenia EC.

Comments: fruit body mostly resupinated but also effused-reflexed; very large, about 1.5 m x 20 cm, about 2-3 mm thick, context thinner than pore layer; small 'pilei' up to 8(12) mm off the substrate; hymenophore with initially distinctly irregular angular, almost labyrinthine pores soon becomes irpiciform to hydnoid (compare Figs. 8. and 10.); smell indistinctive, taste initially indistinctive, after some time slightly unpleasant; 5% KOH reaction on context and pore layer mild, color changed to somewhat darker ocher-beige; SP abundant, white-yellowish with a slight green tint, oac014. No hypha clamps have been observed. All observed traits fit well to expectations for Irpex lacteus except cystidia. The fact that I haven't found conspicuously encrusted cystidia puzzles me.

Spores smooth. Dimensions: 5.1 [5.9 ; 6.2] 7.1 x 2.5 [2.8 ; 2.9] 3.2 microns, Q = 1.9 [2.1 ; 2.2] 2.4; N = 47; C = 95%; Me = 6.1 x 2.8 microns; Qe = 2.2. Basidia dimensions approximately 20 x 4.5 microns.Olympus CH20, NEA 100x/1.25, magnification 1.000 x, oil, in water (spores) and NEA 40x/0.65, magnification 400x, in water, congo red (hymenium, cystidia). AmScope MA500 digital camera.

Herbarium: Mycotheca and lichen herbarium (LJU-Li) of Slovenian Forestry Institute, Večna pot 2, Ljubljana, Index Herbariorum LJF

(1) Personal communication with Mr. Bojam Rot,
(2) A. Bernicchia, Polyporaceaes.l., Fungi Europaei, Vol. 10., Edizioni Candusso (2005), p 296.
(3) L. Ryvarden, R.L. Gilbertson, European Polypores, Fungiflora, Vol.1. (1993), p 352.
(4) G. J. Krieglsteiner (Hrsg.), Die Grosspilze Baden-Württembergs, Band 1, Ulmer (2000), p 329. (5) J. Breitenbach, F. Kraenzlin, Eds., Fungi of Switzerland, Vol.2. Verlag Mykologia (1984), p 176.




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Location: Washington County MN

Amur Cherry tree

Milk-white Toothed Polypore  

Location: Cass County

Milk-white Toothed Polypore  




Created: 10/15/2019

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