his fungus is soil
-
borne. There are many species of
the fungus but Trichoderma aggressivum var.
aggressivum (Trichoderma
harzianum biotype 4
(Th4)) is a major problem particularly to button
mushrooms. It gains entry to growing rooms
primarily through contaminated personnel and
equipment. Other sources include poorly composted
substrate or carryover in rooms that were not
suf
ficiently steamed off. Once introduced, it rapidly
spreads into large disease areas from infection
source. Infection of casing soil can result in serious
losses. Green mold is characterized by dense white
mycelial growth followed by extensive green patches
on casing/compost or mushroom caps. The spores of
the fungus are sticky and can easily be spread by
flies, mites and workers to previously uninfected
area. Red pepper mites are often associated with the
disease.