The Trichoderma species is one of a small group of beneficial fungi being successfully utilised on a commercial scale for biological control of other fungi. This micro-organism is now registered as a biofungicide in many countries including France, UK, Belgium, Switzerland, Sweden. Chile, New Zealand and USA.
In its natural environment, Trichoderma is a resident of the litter and woody debris in humus or associated with plant matter in the soil. It acts as a mycoparasite or saprophyte to establish a niche for itself, often at the expense of other fungi which it may use as an alternative source of nutrients. It has been clearly demonstrated actively parasitising basidiomycetes including Rhizoctonia solani, Armillaria mellea and Chondrostereum purpureum.
Trichoderma has a number of unique properties which have led to its successful commercialisation. Firstly, it is extremely safe, with no recorded adverse reactions through a half-century of investigations and uses. The strains used commercially will not grow above 30°C and therefore present no hazard to humans and livestock.
Secondly, it has a wide range of useful antagonistic and parasitic activity towards other fungi, many of which can be harmful pathogens.
Thirdly, and perhaps most importantly, Trichoderma has immunising and protective qualities when resident in a host. It has an ability to survive long term within the host without causing damage to it while imparting a sort of 'vaccination' effect which discourages other infecting micro-organisms.
This property has led to Trichoderma being called an immunising commensal. Other common commensal organisms include the nitrogen-fixing bacteria in legume roots and the mycorrhizal fungi in pine seedling roots, both of which assist with nutrient uptake.
Trichoderma is probably more at home living in soil than in wood. Many strains of the organism, of which there may be up to 200, can be isolated from soil in nearly all parts of the world. With its extremely rapid growth and copious production of spores, Trichoderma species quickly colonise the substrata of soils, especially after chemical or heat sterilisation treatments.
These growth characteristics are being utilised by incorporating Trichoderma and its close relation Gliocladium virens into potting mixes or glasshouse soil to minimise problems with wilting and damping-off of seedlings caused by fungi such as R. solani, Fusarium and Phytium species.
Notes on Trichoderma research
Trichoderma is a genus of soil-borne beneficial fungi native to certain parts of the world. It includes several species including: T. koningii, T. harzianum, Y. viride, T. polysporum, etc. Most of these species have been known for a number of years to antagonise soil-borne fungal diseases.
Early attempts to inoculate soils with those 'wild type' strains in order to induce disease resistance have been fairly unsuccessful, mainly because those 'wild types' were not capable of colonising the root system, and because they were very susceptible to fungicides. Research was focussed on coming up with strains that can overcome those problems.
Research studies published by Professor Ralph Baker and others indicate that such strains have been developed. The new strains, mainly those of Trichoderma koningii, show a great degree of root competence. They live in symbiosis with the root, living on root exudates, while they form a protective shield around the root biomass. If a pathogenic fungus tries to invade the rhizosphere, it will be stopped by direct attack; a simple cat-and-mouse game.
As the root grows, the film of Trichoderma surrounding it will grow with it. Unlike chemicals, it will not be diluted. Furthermore - those improved strains are very tolerant to fungicides. In other words, they can be used if chemical fungicides must be used, provided a period of a few days is given between the two applications.
Trichoderma species are totally non-parasitic to man, animals and plants. Being biological, they do not leave any harmful chemical residues behind. They are totally organic. Last but not least, Trichoderma species secrete into the rhizosphere some growth stimulants, thereby speeding up seed germination, uniformity of germination, growth, flowering, fruit setting and yields.
The soil-borne diseases that Trichoderma have been found to control include; Fusarium, Rhizoctonia, Phytium, Phytophthora, Sclerotium, Armillaria, Phomopsis, Botrytis, Penicillium, Chondrosterium, etc.
Research has also established that Trichoderma spp. can be applied into the soil during any stage of growth, but preferably early and before any disease incidence takes place. However, in the presence of a disease, applications will have a marked effect on reducing the infection rate.
DATE: January 1996
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