Class: Fungi Imperfect!
Common Names: The Yellow Mat Disease;
Yellow Mold; Confetti Disease.
Latin Root: From “chryso-” meaning
golden and “sporium” or spore.
Habitat & Frequency of Occurence: Saprophytic,
a common mold in soils, and endemic
to composts prepared in direct contact
with the ground. Although Chlysosporium
species naturally inhabit the dung of most
pastured animals and of chickens, today they
are rarely seen in finished mushroom composts
with the development of modern composting
Medium Through Which Contamination
Is Spread: Air; soil; and dung.
Measures of Control: Concrete surface used for composting; isolation of mushroom compost
from areas where untreated soils and raw dung are being stored; and filtration of air during Phase II.
If Chlysosporium occurs before or at the time of casing, salt or a similar alkaline buffer can be applied
to limit the spread of infection.
Macroscopic Appearance: Whitish at first, soon yellowish towards the center and maybe yellowish
overall in color, forming a “corky” layer of tissue between the infected compost and the casing
soil, and inhibiting fruitbody formation.
Microscopic Characteristics: Conidiophores poorly developed, relatively undifferentiated, irregularly
branched, vertically oriented, for the most part resembling and associated with the vegetative
mycelium. Clear, unicellular and often ornamented spores (conidia) develop terminally, either in
short chains or singularly, and measure 3-5 x 4-7 microns.
History, Use and/or Medical Implications: The genus in general does not host many pathogenic
species. One species of special concern is Chlysosporium dermatidis and allies, a mold causing
a skin disease in humans.
Comments: Chrysosporium is an indicator mold whose presence can be traced to compost prepared
on soil. Yellow mat disease is caused by Chrysosporium luteum, a synonym of
Myceliopthora lutea. Another species, Chrysosporium sulphureum, is known as Confetti, and is at
first whitish, then yellowish towards the center. These molds were fairly common in Agaricus
culture previous to 1 940, when composts were prepared directly on soil. With the advent of concrete
composting wharfs, they have all but disappeared. According to Atkins (1 974), this contaminant
is more frequent in cave culture because of the use of ridge beds made directly on the floor of
the cave. Chrysosporium is usually not detected until the first break and retards subsequent flushes.
Moderate To severe outbreaks of either species can adversely affect yields.
Both raw and prepared composts can become infected with this mold. It is thought that the
spores are introduced with the fresh air during the cool down period of the Phase II or from thermotolerant
spores from within the compost itself. Species in this genus can be found on media of poor
nutritional quality. They are generally not seen in spawn culture.
Chrysosporium can be grown for study on a hay infusion agar supplemented with sugar. Many
Chrysosporia have sexual forms in the Gymnoascaceae, an ascomycetous family.
For futher information see:
Carmichael, J.W., 1962 “Chrysosporium and some other Aleuriosporic Hyphomycetes.”.
van Oorshot, CAN., 1980 “A Revision of Chrysosporium and Allied Genera”. Studies in
Mycology No. 20. CBS Publication. Baarn,Nederland,