The fungus Trichoderma is commonly present in nearly all soils. It contains many species and strains, of which some are saprophytic while others are pathogenic to other fungi such as Pythium. Trichoderma is also an opportunistic pathogen to humans and has been reported in the infection of immune-compromised children.
Trichoderma are widely used in agricultural biotechnology and have been already used as biocontrol agents against numerous plant pathogens and quite a few have been developed for commercial use. One species, T. harzianum is used as a fungicide. Trichoderma readily colonizes plant roots and some strains are rhizosphere competent i.e. able to grow on roots and form symbiotic associations with plants. Trichoderma species are resistant to most agricultural chemicals, including fungicides, although individual strains differ in their resistance.
Since many species of Trichoderma are strongly cellulolytic (i.e., they are capable of degrading cellulose since they produce large quantities of the enzyme cellulase), they are very common on cellulosic materials including decaying wood, wood products, textiles, stored cereals and plant foodstuffs. For this reason, they are important spoilage organisms and also cause post-harvest rots of various fruits and vegetables. Trichoderma spp are also important producers of antibiotics and they have been researched extensively for biological control, especially of wood-rotting fungi.
In an indoor environment, Trichoderma spp are commonly found on gypsum board and water saturated wood, wallpaper, carpet and mattress dust, paint, and air-conditioning filters. Generally, Trichoderma species require relatively higher water activity than some other indoor molds such as Penicillium or Aspergillus.
Human infection by species of Trichoderma is limited to individuals with severely weakened immune systems. However, some species such as T. harzianum and T. viride are producers of potent mycotoxins.